refactor(modules)!: de-UO core's copy, and enforce it (phase 3, slice 4)

Phase 3's acceptance criterion 1, made real. Three things, one review:

**The dead bindings.** `client/src/api/client.js` still carried ~190 lines of UO
namespaces — `shard`, `atlas`, the two SSE URLs, `admin.shard/shardOps/atlas/
userShard`, the uo-link and town-crier calls, `player.shard` — with zero core
consumers since slice 3 deleted the views. module-uo vendors its own bindings.
The five assertions core's `apiClient.test.js` made about those URLs moved with
them (Module-uo#5); the encoding test that used `governorHistory` now uses a
core route.

**The copy.** Core is the platform, not one game's site, so its words are
game-neutral now: `About`, `Screenshots`, `Website`'s cards, `Status` (which was
never about a game server at all — it reports site mode), `Wiki`, `SiteFooter`,
the default hero, `brand.js`'s tagline and description, the seeded wiki
categories, and two user-visible NavEditor strings that named a module's admin
screen by its proper name. Which game an instance is for is the operator's to
say — BRAND_* vars, the hero editor, CMS pages — and every real instance already
does: `.env.uomysticmoon.example` sets both brand strings explicitly, so nothing
live changes wording. Wiki page SLUGS are untouched: `seedDefault*` only inserts
what is absent, so renaming one adds a duplicate page to every install.

Also gone: an orphan comment block in `schema.sql` describing the spawn-atlas
tables slice 1 took away, and the two settings rows core seeded for a module
(`game_account_signup`, `uo_link_protocol_3_migrated`). The second was a live
defect — see Module-uo#5, which takes ownership of both and repairs the
one-shot migration core's ordering had disabled.

**The check.** `scripts/checkModuleIdentifiers.js` + `npm run check:modules`,
first step of the server-tests job because it needs no dependencies. It reads
CODE, not prose — file names, import specifiers, route path literals, declared
identifiers and property names — per §5.2, so core's English may still say
"shard" where saying it is worth more than the word costs.

Two things it gets right only because getting them wrong was tried first: it
matches WHOLE WORDS (a substring pass flags `defaultImage`, which contains
"ultIma", four times in this repo), and it strips comments and string bodies in
one character walk (a comment contains quotes, a string contains `//`) — the
`checkImports.js` lesson. It has its own 17-test suite, because a boundary check
that silently stops checking is worse than none. The three §6.5 grandfathering
allowlists are exempt by name, and an exemption that stops matching fails the
build rather than lingering.

BREAKING CHANGE: core no longer seeds `game_account_signup` or
`uo_link_protocol_3_migrated`; module-uo's schema fragment does. An install
running core without module-uo keeps whatever rows it already has and gains no
new ones — nothing in core reads either key.

Deferred to slice 5, deliberately: README.md's 48 UO mentions, including a
`## Shard integration (uo-link)` section and the architecture diagram. That is
documentation, which §5.2 does not cover, and it belongs with the phase-closing
docs pass rather than half-done here.

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

client/src/components/MaintenanceGate.jsx

@@ -2,7 +2,7 @@ import { useAuth } from '../contexts/AuthContext.jsx'
 import { useSite } from '../contexts/SiteContext.jsx'
 import Maintenance from '../routes/public/Maintenance.jsx'
 
-// Wraps the public site. When the shard is in maintenance, visitors see the
+// Wraps the public site. When the site is in maintenance, visitors see the
 // coming-soon page; a logged-in admin sees the real site (live preview).
 export default function MaintenanceGate({ children }) {
   const { mode, loading } = useSite()

client/src/components/SiteFooter.jsx

@@ -40,7 +40,7 @@ export default function SiteFooter() {
           </span>
         </div>
         <div className="site-footer-info">
-          <span>{siteTitle} is an independent private shard project.</span>
+          <span>{siteTitle} is an independent, privately-run game server.</span>
           <span style={{ color: 'var(--dim)', fontSize: '0.84rem' }}>
             <a href={`mailto:${contactEmail}`} style={{ color: 'var(--accent)', textDecoration: 'none' }}>
               {contactEmail}

client/src/components/SiteHeader.jsx

@@ -56,8 +56,8 @@ export default function SiteHeader() {
   // their own (THEMING_AND_NAV.md §7). Two things about the order here:
   //
   //   • the override merge runs FIRST and the feature filter after it, so the
-  //     filter stays the boundary — an override cannot un-hide a shard surface
-  //     this viewer may not see, whatever it says. `pruneNav` applies the same
+  //     filter stays the boundary — an override cannot un-hide a surface this
+  //     viewer may not see, whatever it says. `pruneNav` applies the same
   //     check inside a section and drops one it leaves empty, so a dropdown
   //     never opens onto nothing;
   //   • with no stored row this is the coded NAV, in code order, so an