feat(teams): the reconciler, its four refusal gates, and ctx.teams (API 1.6.0)

Core's projection of the module's Teams, kept in step (docs/website/TEAMS.md
§2.4), plus the two ctx members a module pushes through.

The four gates are the file, and each is invariant 1 in a different costume --
module unavailability is staleness, never emptiness:

  1. getTeams() not ok           -> record the failure, touch NOTHING, return.
  2. ok but empty, core holds >=1 -> quarantine; apply only if the NEXT
                                    authoritative answer, an interval later,
                                    agrees.
  3. getTeamMembers() not ok      -> that Team's roster untouched and stale; the
                                    other Teams sync normally.
  4. ok but zero members, had some -> the same two-strikes quarantine, per Team.

Gates 2 and 4 exist because an authoritative-looking empty answer during a cold
start is the one failure indistinguishable from a real wipe. "Every Team on the
shard disbanded at once" costs one interval to confirm; getting it wrong empties
every roster on the site.

Events are an optimisation, never the source of truth. Member and leadership
deltas apply at once for a Team core already knows; team.created and
team.disbanded only ask for a run. §2.2 scopes archival to an authoritative full
list, so a repeated or spurious disband event costs a reconcile rather than a
Team -- and a Team invented from a delta would have no name, no roster and no
leaders anyway.

Two columns TEAMS.md did not contemplate, both on `teams`:

  - roster_synced_at, because team_sync_state holds one row per MODULE and gate 3
    leaves ONE Team behind while the others sync. Without a per-Team stamp that
    Team's page would report the module's last success as its own -- exactly the
    staleness the gate exists to surface.

  - members_empty_since, gate 4's per-Team quarantine. The twin of
    team_sync_state.pending_empty_since, which is per module and cannot express it.

One real bug found by its own test. The roster upsert was writing is_leader, so a
refused getTeamLeaders() left every member demoted -- the roster had already
written `leader: false` before the authoritative call was even made. §2.5 is
explicit that path 2 is answered by getTeamLeaders(), so is_leader is now set on
INSERT only (seeding a Team so it is not leaderless while that call fails) and
moved afterwards by setLeaders() alone. Two writers for one column was the whole
defect.

MODULE_API_VERSION 1.6.0 on both halves -- they state one contract and a module
declares one coreApi range. The number covers the whole Team surface per Part 11;
the members arrive by phase. registerTeamProvider, ctx.teams.publish and
ctx.teams.reconcile are live. ctx.teams.activity.push (§4, phase 3) and
api.registerSlashCommands (§7.1, phase 7) are present and THROW with a sentence
naming their phase, rather than being absent or silently accepting data into
tables that do not exist yet.

39 tests here, and the ctx surface guard in moduleLoader.test.js updated -- it
caught the addition, which is what it is for. Server 809 passed, client 192
passed, 0 failed.

Refs docs/website/TEAMS.md §2.2, §2.3, §2.4, Part 11, Part 12 phase 2

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

server/test/moduleLoader.test.js

@@ -507,9 +507,13 @@ test('ctx exposes exactly the documented surface, and is frozen', () => {
   // extraction needed it and none could be vendored: an admin action a module
   // performs belongs in core's one audit log, the extension slot needs the user
   // its prefix names, and §2.7 forbids a module reading core's APP_BASE_URL.
+  // API 1.6.0 added `teams` — push, to the pull the team provider answers
+  // (TEAMS.md §2.3). Read-only by omission: a module answers questions about
+  // Teams and never asks them, so there is no getter here to add later by
+  // accident.
   assert.deepEqual(probe.keys, [
     'activity', 'auth', 'db', 'express', 'log', 'middleware', 'moduleId', 'paths',
-    'posts', 'push', 'secretBox', 'settings', 'site', 'uploads', 'users', 'validator',
+    'posts', 'push', 'secretBox', 'settings', 'site', 'teams', 'uploads', 'users', 'validator',
   ])
   //  is core's limiter FACTORY, not a limiter: a module states its own
   // window and cap and takes the plumbing, so there is one express-rate-limit in