feat(rust): Teams from first-party clans (phase 9, protocol 6)

A first-party Rust clan is a Team (R5). This module becomes the site's
Team provider and answers core from the plugin's `clans` board. Design
of record: docs/modules/rust/PLAN.md §24, D47-D58.

- The store: rust_clans, rust_clan_members and rust_clan_boards. A clan's
  identity is <serverId>:<clanId>:<createdMs> (D52), because the game
  restarts clan ids whenever its clan database version changes.
- The provider (D53): getTeams is complete only when every server's
  board is fresh, supported and untruncated. It is partial when some
  are, and refuses when none are. Freshness is judged by the website's
  clock, from when the board's `t` last advanced.
- Only a complete board may mark a clan gone. A board at the game's
  100-clan ceiling (D55), or one with an unreadable row, proves nothing
  about what it leaves out.
- Leadership is diffed board to board and published (D54). The five clan
  events are published as team.* kinds, and written to the Team feed as
  members-only lines (D49).
- Core only writes feed items for a Team it already holds. So the last 10
  minutes of clan events are re-offered on each board refresh, deduped by
  a sha1 key: core clamps a dedupeKey to 40 characters, and a readable key
  would be truncated into collisions.
- projectRoster and the clan page share one audience rule (D48): the
  clan's linked members and staff by default, re-read from the users row.
  The setting lives on Admin > Rust visibility, which also warns about
  uMod Clans (D47) and the ceiling.
- Public: GET servers/:id/clans (the list is public, D58) and
  GET clans/:externalId. The client adds a Clans tab and
  /rust/clans/:externalId, with three module slots for core's notify,
  activity and forum contributions (D56).
- Linking and unlinking an account ask core to reconcile Teams (D57).
- The clan kinds are staff-class in the public feed allowlist.
- PROTOCOL_VERSION is now 6.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E14m6SuuY6i1vASFeGDBeY

server/test/catalogue.test.js

@@ -95,7 +95,7 @@ test('every kind is classified exactly once', () => {
   assert.equal(seen.size, catalogue.PUBLIC_KINDS.length + catalogue.STAFF_KINDS.length)
 })
 
-test('the classification covers exactly the kinds protocol 4 defines', () => {
+test('the classification covers exactly the kinds the protocol defines, through protocol 6', () => {
   // The spec lives in another repository, so the list is restated here rather
   // than parsed — and restating it is the point: adding a kind to the protocol
   // without deciding who may see it has to fail somewhere, and this is where.
@@ -120,9 +120,20 @@ test('the classification covers exactly the kinds protocol 4 defines', () => {
     'account.link.requested',
     'account.unlinked',
     'perm.drift',
+    // Protocol 6 (§12). Clan membership is members-only (D49), so every one of
+    // these is staff-class here and reaches members through core's Team feed.
+    'clan.created',
+    'clan.disbanded',
+    'clan.member.added',
+    'clan.member.left',
+    'clan.member.kicked',
   ]
 
   assert.deepEqual([...catalogue.ALL_KINDS].sort(), [...PROTOCOL_4].sort())
+
+  for (const kind of PROTOCOL_4.filter((k) => k.startsWith('clan.'))) {
+    assert.equal(catalogue.isPublic(kind), false, `${kind} is members-only and must not be public`)
+  }
 })
 
 test('every kind that names a player who was on is behind the presence setting', () => {