feat(rust): identity — a link code from the game, and the Steam id inside core's user page

R1's identity link, site-side, and R13's first extension slot. A player types
/link in game, the plugin hands them a six-character code privately, and they
enter it here; the site records who owns which Steam account, and an operator
sees that on core's own `/admin/users/:id` page.

**The site is the author of record and the game holds nothing.** There is no
per-account store in Rust that survives a wipe, and phase 7 needs the site
authoritative anyway — it pushes permissions INTO the game keyed by Steam id. A
copy in the game would be a second thing to reconcile every wipe, for no question
it could answer better.

## D24 — a code is minted by ONE server, so every server is asked

Nothing in six characters says where it came from. The fleet is asked in turn and
the first `link.ok` wins; the others answer `unknown` and nothing happens there,
because a code is only spent at the server that actually holds it. Asking the
player to pick was rejected: a wrong pick would come back indistinguishable from
a wrong code, and that is the one refusal which must not be ambiguous.

**"Every reachable server refused" is not the same answer as "a server was
unreachable."** Collapsing them tells a player whose server is down that their
code is wrong — so they run /link again on that same server and are told the same
thing for as long as it stays down. `unsure` is that case, and it says to try
again rather than to fetch a new code.

## D23 — a Steam id another account holds is refused, never moved

The primary key is `steam_id`, and it is load-bearing rather than tidy: phase 7
grants permissions against a link and phase 13 hangs entitlements off it, so a
silent move is an account takeover performed by typing six characters. The
refusal names the holder, because the advice is unusable without it. The INSERT
is a plain INSERT for the same reason — `ON DUPLICATE KEY UPDATE` here would BE
that move — and the duplicate-key error is the refusal for the race the check
above cannot close.

The way out is `/unlink` in game, which reaches the site off the ingest feed
rather than through a route (the plugin has no link to delete). D25 adds the
other way out: staff can sever a link from the admin panel, for a player who
cannot reach that Steam account in game.

## The slot, and the hole it found in this repo's own generator

`admin.users.detail` is declared in `module.json` AND registered in `index.js`
AND filled by the chunk — three places, because the server half and the client
half are different registrations that share one name.

`swaggerFragment.js` knew only about tier routers, so the two routes under
`/admin/users/:id` were generated by nothing: a fragment that was internally
consistent and described two routes fewer than the module serves. A slot's mount
is core's and cannot be derived here, so it is a fourth constant beside
`TIER_BASE` — held to account by the frozen-manifest job, which was verified to
catch exactly this by removing the two paths and watching it fail.

## Smaller things worth knowing

- **Core's `useAsync` has no `refresh`.** A counter in the deps is how a page
  re-reads after its own write; it blanks while it re-reads, which is right here
  and is exactly what made it wrong for a poll.
- **Every player-portal nav row needs an `icon`** — core draws one on every row,
  and the client suite says so. This module had no icons file until now, because
  the public header is text buttons.
- The two new frame kinds are STAFF-only. Neither carries a code, but both name a
  Steam id beside a website account's activity, and that join is not a public
  fact about what happened on a server.
- The link code route carries its own rate limiter rather than core's
  `accountChangeLimiter`: this is guessing somebody else's secret, not changing
  your own password, and a shared counter would let one policy set the other.

Protocol 3 on all three declaration sites; 17 new tests, 136 green.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PMH6bw1jXMgbyF3ZWGEzSM

client/src/api.js

@@ -74,6 +74,20 @@ export const playerServers = {
   list: () => req('/player/rust/servers'),
 }
 
+// R1's identity link, from the signed-in player's side.
+//
+// **The code is the whole of what goes up.** The site has no idea which server
+// minted it — nothing in six characters says — so the server half asks each
+// configured server in turn (D24). A page that asked the player to pick would be
+// asking them a question the site can answer itself, and a wrong pick would come
+// back indistinguishable from a wrong code.
+export const playerLinks = {
+  list: () => req('/player/rust/links'),
+  confirm: (code) => req('/player/rust/link', { method: 'POST', body: { code } }),
+  remove: (steamId) =>
+    req(`/player/rust/links/${encodeURIComponent(steamId)}`, { method: 'DELETE' }),
+}
+
 // ── admin ─────────────────────────────────────────────────────────────────
 // **`sidecarToken` goes up and never comes back.** The list answers `hasToken`,
 // and a save that omits the field leaves the stored credential alone — so an
@@ -89,8 +103,23 @@ export const admin = {
     req(`/admin/rust/servers/${encodeURIComponent(id)}/test`, { method: 'POST' }),
 }
 
+// ── the admin.users.detail extension slot ─────────────────────────────────
+//
+// The client half of R13's first slot. Core hands the component a `userId` and
+// NOTHING else — not a client — so an extension builds its own bindings for the
+// routes it registered at the other end (§3.5). These two are the only calls in
+// this file whose path is core's rather than this module's: the resource is
+// core's user, and the module's own segment is the part after it.
+export const adminUserLinks = {
+  list: (userId) => req(`/admin/users/${encodeURIComponent(userId)}/rust/links`),
+  remove: (userId, steamId) =>
+    req(`/admin/users/${encodeURIComponent(userId)}/rust/links/${encodeURIComponent(steamId)}`, {
+      method: 'DELETE',
+    }),
+}
+
 // Exported for the rare caller that needs the base itself — an `<img src>`, a
 // download link, an EventSource. Reach for `request` first.
 export { BASE, query }
 
-export default { servers, playerServers, admin, BASE }
+export default { servers, playerServers, playerLinks, admin, adminUserLinks, BASE }