refactor(client): delete the UO client half (phase 3, slice 3)

35 files and 5,332 lines out — twelve public pages, seven admin views, two
player views, eight components, the two `data/` leaves and the three `lib/`
ones, plus the two tests that came with them. §2.7.1's estimate of 51 files /
~3,700 lines was measured differently and is corrected in the docs PR.

The seams core keeps, each smaller than what it replaced:

Nine rows leave the public header and six leave the admin sidebar, and both
lists are now free of `feature` gates and of `IconShard`. `moduleTitle` already
handled a module page's heading, so the six TITLES entries and the
`/admin/characters` branch of `sectionTitle` simply go.

`/player` had `PlayerCharacters` as its index — a UO page — and rather than name
a replacement or invent a landing screen it now resolves to the first row of the
portal nav this viewer can reach (`firstDestinationFor`, beside
`allowedPathsFor` and reading the BASE nav for the same reason: an override is
presentation and where everybody lands is behaviour). With the module installed
that is still Characters, so a player's first screen after signing in does not
change. Deliberately generic and deliberately not in the portal layout — the
admin index is the same question with a hardcoded answer, and if the two
logged-in areas ever become one this is what serves both.

`game_account_signup` goes with the rest of core's UO prose: the mode list, the
derived public flag, the validation and a Site Settings field whose help text
named Bridge.cfg. The row itself is untouched and module-uo reads it through
ctx.settings — the data stays, the semantics move.

KNOWN BREAK, accepted by the org lead: the shipped Android app reads
`gameAccountSignup` off `/public/settings` (PublicDto.kt:80). The field has a
`= false` default so nothing crashes; the app silently stops offering
game-account creation until it reads the module's `/public/shard/features`
instead. Out of scope here, recorded in the Android plan, and it lands well
before this workstream's cutover reaches `main`.

620 server + 161 client tests. Manifest 158 public + 2 internal, unchanged;
routes.guards unchanged. The OpenAPI spec loses exactly one property, and only
because it was hand-written in swagger.js — regeneration alone would have left
the spec documenting a field core no longer returns.

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

client/src/components/SiteHeader.jsx

@@ -13,13 +13,12 @@ import { useFeatureGate } from '../modules/features.jsx'
 // One consistent top nav for the whole public site. Every page gets the same
 // main links plus an auth-aware entry on the right (Sign in / My Account / Admin).
 //
-// Entries carrying a `feature` are surfaces an admin can disable or gate to a
-// higher audience (Admin -> Shard Visibility). They are hidden when this viewer
-// can't reach them, so we never render a link that would 403. The gate itself is
-// server-side; this is only about not advertising a dead end. Which module
-// answers for a given flag is the registry's business now, not this file's —
-// core registers `useShardFlags` for the ten below and Phase 3 hands them over
-// (modules/featureGate.js).
+// A row may carry a `feature`, naming a surface an installed module can disable
+// or gate to a higher audience; it is hidden when this viewer cannot reach it,
+// so we never render a link that would 403. No CORE row carries one today — the
+// nine that did were UO and left with the client half in slice 3 — but the gate
+// is not dead code: a module's rows join this list and bring their own flags,
+// resolved by the module that registered them (modules/featureGate.js).
 //
 // Exported because Admin -> Navigation edits this list. It stays declared here,
 // with this component as its owner: the editor may only relabel, reorder and
@@ -33,15 +32,6 @@ export const NAV = [
   { label: 'Five on Friday', to: '/site/five-on-friday' },
   { label: 'Newsletter', to: '/site/newsletter' },
   { label: 'Wiki', to: '/wiki' },
-  { label: 'Shard', to: '/site/shard', feature: 'status' },
-  { label: 'Champions', to: '/site/champs', feature: 'champs' },
-  { label: 'Guilds', to: '/site/guilds', feature: 'guilds' },
-  { label: 'Governors', to: '/site/governors', feature: 'governors' },
-  { label: 'Houses', to: '/site/houses', feature: 'houses' },
-  { label: 'Rules', to: '/site/rules', feature: 'ruleset' },
-  { label: 'Atlas', to: '/site/atlas', feature: 'atlas' },
-  { label: 'Leaderboards', to: '/site/leaderboards', feature: 'leaderboards' },
-  { label: 'Market', to: '/site/market', feature: 'market' },
   { label: 'About', to: '/site/about' },
 ]