refactor(modules): move core's UO page content behind the two slots

Core declares site.footer.status and admin.users.detail in main.jsx and fills
both itself, under owner id `core` -- the client twin of registries.registerCore()
and the same trick useShardFlags already uses. The rendered page is unchanged;
what changes is that the content now arrives the way a module's will.

The footer's Shard Status link becomes ShardStatusLink.jsx, and UserDetail's six
UO sections become UserShardSections.jsx. Both are files rather than inline
markup so that the client half of phase 3 deletes a registration and a file
instead of editing a core page under extraction pressure -- which is also what
proves the mechanism before anything depends on it.

The user-detail slot is handed userId and not scope. api.admin.userShard is a UO
binding that leaves core with the client half, so a slot passing it would hand a
module something core is about to delete; an extension builds its own client for
the routes it registered at the other end. Core's own fill now does exactly what
the module will.

Verified in a browser against a real chunk (MODULE_API.md 7.7): a throwaway
module fills both slots and renders its own label and target in the footer with
core's linkStyle, and receives userId on the admin page; a deliberate render
failure is contained to that one spot with the slot named in the console; core's
own fills leave the pages byte-identical to before; and with no module installed
both slots render nothing. Zero CSP reports throughout.

Co-Authored-By: Claude <noreply@anthropic.com>

client/src/components/ShardStatusLink.jsx

@@ -0,0 +1,24 @@
+// ── Core's fill for the `site.footer.status` extension slot ────────────────
+//
+// Phase 3, slice 2 of docs/website/MODULE_SYSTEM.md §2.7.1; the contract is
+// MODULE_API.md §3.7.
+//
+// This is the whole of what used to be four lines inline in SiteFooter.jsx, and
+// it is a file now for one reason: `/site/shard` is a UO page, so the link goes
+// when the client half goes, and core should be deleting a registration rather
+// than editing its footer under extraction pressure.
+//
+// Note what core kept and what it handed over. Core owns the position in the row
+// and the separator around it, and passes `linkStyle` so the row stays visually
+// one row. The label, the destination, and the decision to render at all are
+// this file's — which is exactly the division a module inherits.
+
+import { Link } from 'react-router-dom'
+
+export default function ShardStatusLink({ linkStyle }) {
+  return (
+    <Link to="/site/shard" style={linkStyle}>
+      Shard Status
+    </Link>
+  )
+}

client/src/components/SiteFooter.jsx

@@ -1,5 +1,14 @@
 import { Link } from 'react-router-dom'
 import { useSite } from '../contexts/SiteContext.jsx'
+import Slot from '../modules/Slot.jsx'
+
+const FOOTER_SLOT = 'site.footer.status'
+
+// Handed to the extension rather than left for it to guess. A module rendering
+// its own link in this row should look like the row, and the alternative is
+// every module restating core's colours and then drifting from them the next
+// time this footer is themed.
+const LINK_STYLE = { color: 'var(--accent)', textDecoration: 'none' }
 
 export default function SiteFooter() {
   const { contactEmail, siteTitle } = useSite()
@@ -36,10 +45,14 @@ export default function SiteFooter() {
             <a href={`mailto:${contactEmail}`} style={{ color: 'var(--accent)', textDecoration: 'none' }}>
               {contactEmail}
             </a>
-            &nbsp;·&nbsp;
+            {/* A module's spot in the footer, and core supplies only the
-            <Link to="/site/shard" style={{ color: 'var(--accent)', textDecoration: 'none' }}>
+                position and the styling: the label, the target and whether
-              Shard Status
+                anything renders at all are the module's (MODULE_API.md §3.7).
-            </Link>
+                The separator goes through `wrap` rather than sitting beside the
+                slot, so it shares the extension's fate — no module installed and
+                a module whose link throws both render nothing here, rather than
+                the second leaving a stray middot behind. */}
+            <Slot name={FOOTER_SLOT} linkStyle={LINK_STYLE} wrap={(link) => <>&nbsp;·&nbsp;{link}</>} />
             &nbsp;·&nbsp;
             <Link to="/admin/login" style={{ color: '#5d6b7d', textDecoration: 'none' }}>
               Admin

client/src/main.jsx

@@ -3,8 +3,10 @@ import { createRoot } from 'react-dom/client'
 import { BrowserRouter } from 'react-router-dom'
 import App from './App.jsx'
 import { publishSharedDependencies } from './modules/shared.js'
-import { registerFeatureProvider } from './modules/registry.js'
+import { declareSlot, registerExtension, registerFeatureProvider } from './modules/registry.js'
 import { useShardFlags } from './lib/useShardFeatures.js'
+import ShardStatusLink from './components/ShardStatusLink.jsx'
+import UserShardSections from './routes/admin/views/UserShardSections.jsx'
 import './styles/theme.css'
 
 // Publish window.__rg BEFORE rendering and before any module chunk evaluates.
@@ -28,6 +30,34 @@ publishSharedDependencies()
 // for them by the name they will always have had.
 registerFeatureProvider('core', 'uo', useShardFlags)
 
+// ── Extension slots (MODULE_API.md §3.7) ───────────────────────────────────
+//
+// Declared HERE, in core's own bundle, which is what makes the ordering a fact
+// rather than a hope: module chunks are deferred scripts the shell injects after
+// this one (§3.1), so a module can never reach registerExtension before the slot
+// it names exists. "Unknown slot" therefore always means a typo or a version
+// skew, never a load-order accident — which is why that case throws.
+//
+// Both slots are named for a PLACE, not for a meaning. `site.footer.status` is
+// the spot in the footer's info row, not a declaration that core knows what a
+// game server's status is; the label, the target and whether anything renders at
+// all belong to whoever fills it. A slot typed by its content would put game
+// semantics back into core, which is the thing Phase 3 takes out.
+declareSlot('site.footer.status')
+// Deliberately the same name as the server's slot (MODULE_API.md §2.4): one
+// resource, one extension point, two halves. The module with routes under
+// /api/v1/admin/users/:id is the module with something to show on that page.
+declareSlot('admin.users.detail')
+
+// And core fills both itself, under owner id `core`, with the components that
+// were inline in SiteFooter.jsx and UserDetail.jsx until this slice. The page
+// renders exactly what it rendered before, and the mechanism is exercised by
+// core's own content from the day it lands rather than first proved by the
+// change that depends on it. Slice 3 deletes these three lines and the two files
+// they name, and the module registers the same two slots on its way in.
+registerExtension('core', 'site.footer.status', ShardStatusLink)
+registerExtension('core', 'admin.users.detail', UserShardSections)
+
 // Render on DOMContentLoaded rather than immediately, and that is the one line
 // of core's boot the module system changes.
 //

client/src/routes/admin/views/UserDetail.jsx

@@ -1,17 +1,16 @@
-import { useCallback, useEffect, useMemo, useState } from 'react'
+import { useCallback, useEffect, useState } from 'react'
 import { useParams, Link } from 'react-router-dom'
 import { Loading, ErrorState } from '../../../components/PageState.jsx'
 import { useAsync } from '../../../lib/useAsync.js'
-import { dateTime, ago } from '../../../lib/format.js'
+import { dateTime } from '../../../lib/format.js'
 import { api } from '../../../api/client.js'
-import CharacterStats from '../../../components/CharacterStats.jsx'
+import Slot from '../../../modules/Slot.jsx'
-import GameAccounts from '../../../components/GameAccounts.jsx'
-import VendorSales from '../../../components/VendorSales.jsx'
 
-// Admin read-only view of one user's shard (uo-link) footprint: linked game
+// Admin view of one user: who they are, their security posture (trusted devices
-// accounts + character rosters, currently-online characters, houses (incl.
+// and MFA), and then whatever the installed module contributes about them —
-// IDOC) and recent vendor sales — everything scoped to that user's accounts.
+// today core's own UO footprint, via the `admin.users.detail` extension slot
-// Reached from the Users table's "View" action; Edit stays a separate modal.
+// (MODULE_API.md §3.7). Reached from the Users table's "View" action; Edit stays
+// a separate modal.
 
 const ROLE_BADGE = {
   admin: 'badge-admin',
@@ -28,114 +27,6 @@ function SectionTitle({ children }) {
   )
 }
 
-// Currently-online characters on the user's accounts, with where they are. The
-// per-character Online/Offline badge lives in the roster; this adds location.
-function OnlineNow({ scope }) {
-  const { data } = useAsync(() => scope.online(), [scope])
-  if (!data) return null
-  return (
-    <section style={{ borderTop: '1px solid var(--line-soft)', marginTop: 30, paddingTop: 22 }}>
-      <SectionTitle>Online now</SectionTitle>
-      {data.length === 0 ? (
-        <p className="sans dim" style={{ margin: 0, fontSize: '0.86rem' }}>No characters online right now.</p>
-      ) : (
-        <ul style={{ listStyle: 'none', margin: 0, padding: 0, display: 'flex', flexDirection: 'column', gap: 8 }}>
-          {data.map((c) => (
-            <li key={c.serial} className="sans" style={{ display: 'flex', justifyContent: 'space-between', gap: 12, fontSize: '0.9rem', color: 'var(--ink)' }}>
-              <span style={{ display: 'inline-flex', alignItems: 'center', gap: 8, minWidth: 0 }}>
-                <span style={{ width: 8, height: 8, borderRadius: '50%', background: '#7fd0a4', boxShadow: '0 0 6px #7fd0a4', flex: 'none' }} />
-                <span style={{ color: 'var(--head)' }}>{c.name || '(unnamed)'}</span>
-              </span>
-              <span className="dim" style={{ flex: 'none', fontSize: '0.8rem' }}>
-                {c.map != null ? `map ${c.map} · ${c.x}, ${c.y}` : '—'}
-              </span>
-            </li>
-          ))}
-        </ul>
-      )}
-    </section>
-  )
-}
-
-// Shard "standing": city governorships held and guilds led by this user's
-// accounts (both reliable current-state lookups). Renders nothing when empty.
-function Standing({ scope }) {
-  const { data } = useAsync(() => scope.standing(), [scope])
-  if (!data) return null
-  const govs = data.governorOf || []
-  const guilds = data.guildsLed || []
-  if (govs.length === 0 && guilds.length === 0) return null
-  return (
-    <section style={{ borderTop: '1px solid var(--line-soft)', marginTop: 30, paddingTop: 22 }}>
-      <SectionTitle>Standing</SectionTitle>
-      <div style={{ display: 'flex', flexWrap: 'wrap', gap: 8 }}>
-        {govs.map((g) => (
-          <span key={`gov-${g.city}`} className="sans" style={{ fontSize: '0.78rem', padding: '4px 10px', borderRadius: 999, border: '1px solid #c9a24b55', color: '#c9a24b' }}>
-            Governor of {g.city}
-          </span>
-        ))}
-        {guilds.map((g) => (
-          <span key={`guild-${g.id}`} className="sans" style={{ fontSize: '0.78rem', padding: '4px 10px', borderRadius: 999, border: '1px solid var(--accent)', color: 'var(--accent)' }}>
-            Guildmaster{g.abbr ? `, [${g.abbr}]` : ''} {g.name}
-          </span>
-        ))}
-      </div>
-    </section>
-  )
-}
-
-// One house row — the many optional detail fields are gathered here so the
-// Houses list stays a simple map.
-function HouseRow({ house: h }) {
-  const location = h.region || (h.map != null ? `map ${h.map}` : 'unknown')
-  const coords = h.x != null ? ` · ${h.x}, ${h.y}` : ''
-  const owner = h.ownerAcct ? ` · ${h.ownerAcct}` : ''
-  const shares = h.coOwners || h.friends ? ` · ${h.coOwners || 0} co-owners, ${h.friends || 0} friends` : ''
-  return (
-    <li
-      style={{ display: 'flex', justifyContent: 'space-between', gap: 12, alignItems: 'baseline', padding: '12px 14px', border: '1px solid var(--line)', borderRadius: 10, background: 'rgba(255,255,255,0.02)' }}
-    >
-      <div style={{ minWidth: 0 }}>
-        <div className="sans" style={{ color: 'var(--head)', fontSize: '0.95rem' }}>
-          {h.name || 'Unnamed house'}
-          {h.isIdoc && <span className="badge" style={{ marginLeft: 8, background: '#5b2020', color: '#f0c8c2' }}>IDOC</span>}
-        </div>
-        <div className="sans dim" style={{ fontSize: '0.78rem', marginTop: 2 }}>
-          {location}
-          {coords}
-          {owner}
-          {shares}
-        </div>
-      </div>
-      <div className="sans dim" style={{ flex: 'none', fontSize: '0.78rem', textAlign: 'right' }}>
-        {(h.decay || h.stage) ? <div style={{ color: h.isIdoc ? '#e0928a' : 'var(--muted)' }}>{h.decay || h.stage}</div> : null}
-        {h.price != null ? <div style={{ fontVariantNumeric: 'tabular-nums' }}>{Number(h.price).toLocaleString()} gp</div> : null}
-        {h.lastRefreshed ? <div>refreshed {ago(h.lastRefreshed)}</div> : null}
-      </div>
-    </li>
-  )
-}
-
-// Houses owned by the user's accounts, IDOC first (flagged).
-function Houses({ scope }) {
-  const { data } = useAsync(() => scope.houses(), [scope])
-  if (!data) return null
-  return (
-    <section style={{ borderTop: '1px solid var(--line-soft)', marginTop: 30, paddingTop: 22 }}>
-      <SectionTitle>Houses</SectionTitle>
-      {data.length === 0 ? (
-        <p className="sans dim" style={{ margin: 0, fontSize: '0.86rem' }}>No houses recorded for this user’s accounts.</p>
-      ) : (
-        <ul style={{ listStyle: 'none', margin: 0, padding: 0, display: 'flex', flexDirection: 'column', gap: 10 }}>
-          {data.map((h) => (
-            <HouseRow key={h.serial} house={h} />
-          ))}
-        </ul>
-      )}
-    </section>
-  )
-}
-
 // Admin security controls for one user: their trusted devices (view + revoke) and
 // an MFA reset for a locked-out user. Every action is audit-logged server-side.
 function SecurityAdmin({ userId }) {
@@ -244,25 +135,8 @@ function SecurityAdmin({ userId }) {
   )
 }
 
-function ShardSections({ scope }) {
-  return (
-    <>
-      <CharacterStats scope={scope} />
-      <SectionTitle>Linked accounts &amp; characters</SectionTitle>
-      <GameAccounts scope={scope} readOnly moderation onUnlink={scope.unlink} charTo={(serial) => `/admin/characters/${serial}`} />
-      <Standing scope={scope} />
-      <OnlineNow scope={scope} />
-      <Houses scope={scope} />
-      <VendorSales fetchSales={scope.sales} />
-    </>
-  )
-}
-
 export default function UserDetail() {
   const { id } = useParams()
-  // Memoize so the child components' effects (keyed on `scope`) don't refetch
-  // on every render.
-  const scope = useMemo(() => api.admin.userShard(id), [id])
   const { loading, error, data: user } = useAsync(() => api.admin.getUser(id), [id])
 
   if (loading) return <Loading />
@@ -296,7 +170,10 @@ export default function UserDetail() {
       </div>
 
       <SecurityAdmin userId={id} />
-      <ShardSections scope={scope} />
+      {/* Whatever the installed module has to say about this user, or nothing
+          at all. Core's own UO sections fill it today (UserShardSections.jsx,
+          registered in main.jsx) — MODULE_API.md §3.7. */}
+      <Slot name="admin.users.detail" userId={id} />
     </section>
   )
 }

client/src/routes/admin/views/UserShardSections.jsx

@@ -0,0 +1,163 @@
+// ── Core's fill for the `admin.users.detail` extension slot ────────────────
+//
+// Phase 3, slice 2 of docs/website/MODULE_SYSTEM.md §2.7.1. Every section below
+// is UO, and every one of them leaves core with the client half in slice 3 —
+// this file exists so that when they do, core deletes a registration and a file
+// instead of unpicking a page.
+//
+// Core registers it through the same seam a module uses
+// (`registerExtension('core', …)` in main.jsx), which is the client twin of the
+// server's `registries.registerCore()` and the same trick `useShardFlags`
+// already uses for the feature seam. The mechanism is therefore exercised by
+// core's own content from the day it lands, rather than first proved by the
+// change that depends on it.
+//
+// The slot hands over `userId` and nothing else — deliberately, not `scope`.
+// `api.admin.userShard` is a UO binding that leaves core in slice 3, so a slot
+// that passed it would be handing a module something core is about to delete.
+// An extension builds its own client for the routes it registered at the other
+// end (MODULE_API.md §3.5), and this file does exactly what the module will.
+
+import { useMemo } from 'react'
+import { useAsync } from '../../../lib/useAsync.js'
+import { ago } from '../../../lib/format.js'
+import { api } from '../../../api/client.js'
+import CharacterStats from '../../../components/CharacterStats.jsx'
+import GameAccounts from '../../../components/GameAccounts.jsx'
+import VendorSales from '../../../components/VendorSales.jsx'
+
+// Its own copy, not an export from UserDetail.jsx: six lines of presentational
+// furniture that is not in the §3.4 kit, so a module filling this slot would
+// vendor the same thing. Core's copy stays behind with core's own security
+// panel, which is the other caller.
+function SectionTitle({ children }) {
+  return (
+    <div className="field-label" style={{ marginBottom: 12, marginTop: 4 }}>
+      {children}
+    </div>
+  )
+}
+
+// Currently-online characters on the user's accounts, with where they are. The
+// per-character Online/Offline badge lives in the roster; this adds location.
+function OnlineNow({ scope }) {
+  const { data } = useAsync(() => scope.online(), [scope])
+  if (!data) return null
+  return (
+    <section style={{ borderTop: '1px solid var(--line-soft)', marginTop: 30, paddingTop: 22 }}>
+      <SectionTitle>Online now</SectionTitle>
+      {data.length === 0 ? (
+        <p className="sans dim" style={{ margin: 0, fontSize: '0.86rem' }}>No characters online right now.</p>
+      ) : (
+        <ul style={{ listStyle: 'none', margin: 0, padding: 0, display: 'flex', flexDirection: 'column', gap: 8 }}>
+          {data.map((c) => (
+            <li key={c.serial} className="sans" style={{ display: 'flex', justifyContent: 'space-between', gap: 12, fontSize: '0.9rem', color: 'var(--ink)' }}>
+              <span style={{ display: 'inline-flex', alignItems: 'center', gap: 8, minWidth: 0 }}>
+                <span style={{ width: 8, height: 8, borderRadius: '50%', background: '#7fd0a4', boxShadow: '0 0 6px #7fd0a4', flex: 'none' }} />
+                <span style={{ color: 'var(--head)' }}>{c.name || '(unnamed)'}</span>
+              </span>
+              <span className="dim" style={{ flex: 'none', fontSize: '0.8rem' }}>
+                {c.map != null ? `map ${c.map} · ${c.x}, ${c.y}` : '—'}
+              </span>
+            </li>
+          ))}
+        </ul>
+      )}
+    </section>
+  )
+}
+
+// Shard "standing": city governorships held and guilds led by this user's
+// accounts (both reliable current-state lookups). Renders nothing when empty.
+function Standing({ scope }) {
+  const { data } = useAsync(() => scope.standing(), [scope])
+  if (!data) return null
+  const govs = data.governorOf || []
+  const guilds = data.guildsLed || []
+  if (govs.length === 0 && guilds.length === 0) return null
+  return (
+    <section style={{ borderTop: '1px solid var(--line-soft)', marginTop: 30, paddingTop: 22 }}>
+      <SectionTitle>Standing</SectionTitle>
+      <div style={{ display: 'flex', flexWrap: 'wrap', gap: 8 }}>
+        {govs.map((g) => (
+          <span key={`gov-${g.city}`} className="sans" style={{ fontSize: '0.78rem', padding: '4px 10px', borderRadius: 999, border: '1px solid #c9a24b55', color: '#c9a24b' }}>
+            Governor of {g.city}
+          </span>
+        ))}
+        {guilds.map((g) => (
+          <span key={`guild-${g.id}`} className="sans" style={{ fontSize: '0.78rem', padding: '4px 10px', borderRadius: 999, border: '1px solid var(--accent)', color: 'var(--accent)' }}>
+            Guildmaster{g.abbr ? `, [${g.abbr}]` : ''} {g.name}
+          </span>
+        ))}
+      </div>
+    </section>
+  )
+}
+
+// One house row — the many optional detail fields are gathered here so the
+// Houses list stays a simple map.
+function HouseRow({ house: h }) {
+  const location = h.region || (h.map != null ? `map ${h.map}` : 'unknown')
+  const coords = h.x != null ? ` · ${h.x}, ${h.y}` : ''
+  const owner = h.ownerAcct ? ` · ${h.ownerAcct}` : ''
+  const shares = h.coOwners || h.friends ? ` · ${h.coOwners || 0} co-owners, ${h.friends || 0} friends` : ''
+  return (
+    <li
+      style={{ display: 'flex', justifyContent: 'space-between', gap: 12, alignItems: 'baseline', padding: '12px 14px', border: '1px solid var(--line)', borderRadius: 10, background: 'rgba(255,255,255,0.02)' }}
+    >
+      <div style={{ minWidth: 0 }}>
+        <div className="sans" style={{ color: 'var(--head)', fontSize: '0.95rem' }}>
+          {h.name || 'Unnamed house'}
+          {h.isIdoc && <span className="badge" style={{ marginLeft: 8, background: '#5b2020', color: '#f0c8c2' }}>IDOC</span>}
+        </div>
+        <div className="sans dim" style={{ fontSize: '0.78rem', marginTop: 2 }}>
+          {location}
+          {coords}
+          {owner}
+          {shares}
+        </div>
+      </div>
+      <div className="sans dim" style={{ flex: 'none', fontSize: '0.78rem', textAlign: 'right' }}>
+        {(h.decay || h.stage) ? <div style={{ color: h.isIdoc ? '#e0928a' : 'var(--muted)' }}>{h.decay || h.stage}</div> : null}
+        {h.price != null ? <div style={{ fontVariantNumeric: 'tabular-nums' }}>{Number(h.price).toLocaleString()} gp</div> : null}
+        {h.lastRefreshed ? <div>refreshed {ago(h.lastRefreshed)}</div> : null}
+      </div>
+    </li>
+  )
+}
+
+// Houses owned by the user's accounts, IDOC first (flagged).
+function Houses({ scope }) {
+  const { data } = useAsync(() => scope.houses(), [scope])
+  if (!data) return null
+  return (
+    <section style={{ borderTop: '1px solid var(--line-soft)', marginTop: 30, paddingTop: 22 }}>
+      <SectionTitle>Houses</SectionTitle>
+      {data.length === 0 ? (
+        <p className="sans dim" style={{ margin: 0, fontSize: '0.86rem' }}>No houses recorded for this user’s accounts.</p>
+      ) : (
+        <ul style={{ listStyle: 'none', margin: 0, padding: 0, display: 'flex', flexDirection: 'column', gap: 10 }}>
+          {data.map((h) => (
+            <HouseRow key={h.serial} house={h} />
+          ))}
+        </ul>
+      )}
+    </section>
+  )
+}
+export default function UserShardSections({ userId }) {
+  // Memoized so the child components' effects (keyed on `scope`) don't refetch
+  // on every render — the same reason UserDetail memoized it before this moved.
+  const scope = useMemo(() => api.admin.userShard(userId), [userId])
+  return (
+    <>
+      <CharacterStats scope={scope} />
+      <SectionTitle>Linked accounts &amp; characters</SectionTitle>
+      <GameAccounts scope={scope} readOnly moderation onUnlink={scope.unlink} charTo={(serial) => `/admin/characters/${serial}`} />
+      <Standing scope={scope} />
+      <OnlineNow scope={scope} />
+      <Houses scope={scope} />
+      <VendorSales fetchSales={scope.sales} />
+    </>
+  )
+}