fix(rust): answer refusals in the field core reads, and show the name the game last saw

The two defects the phase 6 browser walk found and #6 described but did not
carry. They were written, walked and left uncommitted; `edge` still has the
shapes the walk condemned.

**Every refusal sentence was invisible.** Core's request primitive reads one
field — `(data && data.message) || res.statusText` — and this module has
answered `{ error: … }` since phase 1. It got away with it because every
failure until phase 6 landed in `ErrorState` on a page whose whole content was
missing, where a generic sentence is honest. A form is different: the sentence
IS the outcome, and the link page showed *Service Unavailable* for all four of
the refusals phase 6 exists to write. All 23 bodies now answer in `message` —
core's `Error` schema, which these routes' own `#swagger.responses` already
referenced, so the annotations stop being a claim the handlers contradict.

`test/errorShape.test.js` drives each outcome rather than grepping for the
field, and asserts the half that is easy to leave behind: a body carrying BOTH
fields renders correctly in a browser and keeps the wrong shape alive for the
next route that copies it.

**The player saw a stale name.** `/player/rust` showed the name recorded at
link time while the admin panel showed the one the game last saw — the same
person labelled two ways on one site, because a Rust name changes on a whim and
only the admin read joined `rust_players`. A LEFT JOIN, because an account can
be linked and never played on.

123 server tests, 39 client tests, `check:imports`, `check:bundle`,
`check:swagger`, `check:externals` — all green.

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

server/test/links.test.js

@@ -274,3 +274,21 @@ test('the in-game unlink is scoped by Steam id alone, because that is the author
   assert.ok(!del.sql.includes('user_id'))
   assert.deepEqual(del.params, ['7656'])
 })
+
+test('a player sees the name the GAME last saw, not the one they linked under', async () => {
+  withCore({ select: [[{ steamId: '7656', userId: 4, name: 'Wanderer-old', playerName: 'Wanderer', serverId: 'a', linkedAt: 'x' }]] })
+  const links = require('../model/links/links.model')
+
+  const [link] = await links.listForUser(4)
+
+  // Found in a browser: staff saw `Wanderer` on the admin panel and the player
+  // saw `Wanderer-old` on their own page — the same person, labelled two ways on
+  // one site, because a Rust name changes on a whim and only one of the two reads
+  // was joining `rust_players`.
+  assert.equal(link.name, 'Wanderer')
+
+  // And the fallback still holds for a link whose account has never played.
+  withCore({ select: [[{ steamId: '7656', userId: 4, name: 'Wanderer-old', playerName: null, linkedAt: 'x' }]] })
+  const again = require('../model/links/links.model')
+  assert.equal((await again.listForUser(4))[0].name, 'Wanderer-old')
+})