docs(website): record the PR 4 admin router split and the end of admin.routes.js

Covers website PR 4, the last admin split PR: shard (16), uo-link (5), email
(6), discord-bot (2), settings (2) and dashboard/site-mode (2) leave the
residual file, which is deleted. The admin group is fully split.

API_V2_PLAN.md gains a "PR 4 — as landed" section recording the two decisions a
reviewer would otherwise have to reconstruct: dashboard.router.js is mounted at
the group root (the single relaxation of the mount-at-a-prefix rule, safe only
because it declares no router-level middleware), and /shard keeps two gate tiers
in one router because prefix ownership beats swagger-tag grouping. Sequencing
item 7 is marked landed; PR 5 (public/player/auth) is the only split PR left.

BACKEND_DESIGN.md §2 gets the six new routers in the folder tree and drops the
residual entry; §4's /admin preamble now describes the ops/config gates instead
of pointing at a file that no longer exists.

WIKI_UPGRADE.md's two links into admin.routes.js are repointed at wiki.router.js
and admin/imageUpload.js.

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

website/API_V2_PLAN.md

@@ -421,6 +421,63 @@ Notes:
   capabilities that read alike** — the latter stays with `shard` in PR 4. Same trap as PR 2's
   `activity` / `dashboard` / `bot-activity` trio.
 
+### PR 4 — as landed
+
+`shard`, `uo-link`, `email`, `discord-bot`, `settings` and `dashboard`/`site-mode` — the whole residual
+33. **`admin.routes.js` is deleted**, so the admin group is fully split and every one of its 110 routes
+is declared in a capability router.
+
+| Router | Routes | Prefix | Extra gate |
+|---|---|---|---|
+| `shard.router.js` | 16 | `/admin/shard` | none on the 7 self-service routes; `modAccess` per route on the 9 staff ops |
+| `uoLink.router.js` | 5 | `/admin/uo-link` | `adminOnly` per route |
+| `email.router.js` | 6 | `/admin/email` | `adminOnly` per route |
+| `discordBot.router.js` | 2 | `/admin/discord-bot` | `adminOnly` per route |
+| `settings.router.js` | 2 | `/admin/settings` | `adminOnly` per route |
+| `dashboard.router.js` | 2 | **group root** (`/dashboard`, `/site-mode`) | `adminOnly` per route on `/site-mode` only |
+| ~~`admin.routes.js`~~ | — | deleted | — |
+
+16 + 5 + 6 + 2 + 2 + 2 = 33. All four gates zero-diff: `routes.manifest.json` (200 public + 2
+internal), `routes.guards.json`, `swagger-output.json` (198 operations), and
+`docs/website/api-route-inventory.json` was already in sync. 434 server tests green.
+
+Notes:
+
+- **`dashboard.router.js` is mounted at the group root, not a prefix — the one relaxation of the
+  "always mount at a prefix" rule, and it is deliberate.** `GET /dashboard` and `PUT /site-mode` own no
+  common path segment, so a prefix mount would mean two one-route files instead of the single file the
+  target tree calls for. It is safe **only** because the file declares no router-level middleware: a
+  bare `use(gate)` in a root-mounted router runs for every request passing through toward another
+  mount and would 403 an editor on an unrelated route (the PR 1 finding). The file says so in a
+  comment, because the next person to add a gate there is the one who needs to know.
+- **`/shard` is the first prefix where two tiers share one router**, and it is why prefix ownership
+  beats swagger-tag grouping. The 7 self-service routes (`link`, `accounts`, `roster/:account`,
+  `vendors/:account`, `char/:serial`, `sales`, `POST account`) are tagged `Admin · Account`, run with
+  no gate beyond the shared `staffOnly`, and are served by the very same `player/shard.controller`
+  handlers as `/player/shard` — staff are a superset of players, and the controller keys off
+  `req.user.id`. The 9 in-game ops are tagged `Admin · Shard` and carry `modAccess`. Splitting them by
+  tag would put two routers under one prefix for no gain; instead one router owns `/shard` and gates
+  per route. The tag mismatch stays, on the PR 1 and PR 3 precedent: retagging is a real spec diff and
+  belongs in a PR that is about tags.
+- **No gate moved to router level anywhere in this PR.** Every `adminOnly` in the residual file was
+  per-route, and `modAccess` on `/shard` must stay per-route because half that router must *not* have
+  it. This keeps the per-route handler count intact — the one number `routes.guards.json` can actually
+  check, since `requireRole(...)` returns an anonymous arrow.
+- **The `/:param` shadowing check was run again and is clean**, since the manifest sorts and therefore
+  cannot see declaration order. Introspecting the built stack, all 110 admin routes and all 59 literal
+  admin paths dispatch to their own layer — nothing is captured first by a `:param` sibling. The
+  near-misses worth naming: `GET /shard/pages` (help-page queue) sits alongside
+  `POST /shard/pages/:id/respond|close`, and `POST /shard/towncrier` alongside
+  `DELETE /uo-link/towncrier/:id` — different depths and methods, so neither collides.
+- **Deleting the file left dangling `see admin.routes.js` pointers**, which were repointed in the same
+  PR: `botActivity.controller.js` → `botActivity.router.js`, `moderation.controller.js` →
+  `moderation.router.js`, `announceJobs.logic.js`'s town-crier cap mirror → `admin/uoLink.router.js`,
+  and the "route paths sit on the line *after* `adminRouter.get(`" rationale in
+  `scripts/routeManifest.js`, `README.md` and `pr-checks.yml` was generalized (it was never about that
+  one file).
+- **`/admin/shard/pages` vs `/admin/pages` stayed separate**, as PR 3 flagged: the former is the
+  in-game help-page (support) queue and belongs to `shard`; the latter is the CMS page builder.
+
 ### The swagger path-normalization prerequisite (landed before PR 1)
 
 swagger-autogen builds a path by string-concatenating the mount prefix with the route argument, so a
@@ -533,8 +590,8 @@ deliberate `+1` in the manifest — which is exactly the mechanism working as de
 6. **PR 3 — admin (content):** `posts`, `pages`, `wiki`, `uploads`. ✅ landed
 7. **PR 4 — admin (ops/config):** `shard`, `uo-link`, `email`, `discord-bot`, `settings`, `site-mode`,
    `dashboard`. (`activity` went with PR 2 — see § PR 2 — as landed.) **This is the whole residual
-   file** — `admin.routes.js` is deleted here, not by PR 5.
-8. **PR 5 — `public/*` + `player/*`** (and the residual `auth/*` grouping).
+   file** — `admin.routes.js` is deleted here, not by PR 5. ✅ landed
+8. **PR 5 — `public/*` + `player/*`** (and the residual `auth/*` grouping). **The only split PR left.**
 
 Each PR: **zero-line diff in `routes.manifest.json`**, server tests green
 (`cd website/server && npm test`), Swagger regenerated, matching `docs/` edit, Conventional Commit,