feat(triage): 3-state delivery + admin observer + admin cache

Triage channels now compute a 3-state delivery decision per recipient
(wake / observer / skip) instead of the binary wakeup flag, and route
according to:

  1. author never gets back their own message            → skip
  2. wake_mapping member (on-duty)                       → wake
  3. mention (NEW: was 'skip' for triage before)         → wake
  4. Center-scoped admin (at most 1)                     → observer
  5. anyone else                                         → skip
                                                         (was 'deliver wake=false')

Skipping means the websocket emit is omitted entirely — the recipient's
openclaw plugin never sees the message and the agent's session stays
free of background noise. Observer means delivered with wakeup=false
(silent UI / no model dispatch on the plugin side).

## What this PR ships

### realtime/realtime.gateway.ts
- new `computeDelivery()` returns DeliveryDecision = 'wake'|'observer'|'skip'
- old `computeWakeup()` kept as a deprecated wrapper for callers that
  still want the boolean answer (treats observer + skip as false)
- `emitMessageCreated` accepts `adminUserId?: string|null` and now
  short-circuits on 'skip' (no socket emit at all)
- general kept its current behavior; custom kept its current behavior
  (members not in wake_mapping become observer instead of `wake=false`)
  — the user-visible bit is just that the response field is the same
  `wakeup: boolean`; the explicit 'skip' is new for triage

### common/center-auth.ts
- `fetchAdminEmail()` calls GET `${center}/auth/admin-email` with the
  existing x-api-key (same auth as introspect/resolve-names). Returns
  `{email, userId}` or `null` on either "no admin" or any error

### common/admin-cache.service.ts (NEW)
- `AdminCacheService` — in-memory cache, 1-day TTL, lazy refresh.
  `get(force=true)` bypasses TTL for cli-triggered refresh
- exposed by MessagingModule

### messaging/messaging.controller.ts
- non-rotating branch threads `adminUserId` into emitMessageCreated

### cli/admin-refresh.ts (NEW)
- `node dist/cli/admin-refresh.js` — force-refresh cache and print
  before/after JSON. Use after a Center `user set-admin` so triage
  delivery picks up the new admin without waiting for 24h TTL

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/cli/admin-refresh.ts

@@ -0,0 +1,39 @@
+// Operator convenience: force-refresh the in-memory Center admin cache
+// without waiting for the 1-day TTL. Used after `center user set-admin`
+// to make new admin visible immediately to triage delivery.
+//
+// Usage (inside the deployed container):
+//   docker exec fabric-backend-guild node dist/cli/admin-refresh.js
+//
+// Prints the (possibly null) result as JSON. Exit 0 always — a "no
+// admin" outcome is a valid state, not an error.
+
+import 'reflect-metadata';
+import { NestFactory } from '@nestjs/core';
+import { AppModule } from '../app.module.js';
+import { AdminCacheService } from '../common/admin-cache.service.js';
+
+async function main() {
+  const app = await NestFactory.createApplicationContext(AppModule, { logger: ['error', 'warn'] });
+  try {
+    const cache = app.get(AdminCacheService);
+    const before = cache.snapshot();
+    const after = await cache.get(true);
+    process.stdout.write(
+      JSON.stringify({
+        ok: true,
+        before,
+        after,
+        changed: JSON.stringify(before) !== JSON.stringify(after),
+      }) + '\n',
+    );
+  } finally {
+    await app.close();
+  }
+}
+
+void main().catch((error: unknown) => {
+  const message = error instanceof Error ? error.message : 'unknown error';
+  process.stderr.write(JSON.stringify({ ok: false, error: message }) + '\n');
+  process.exit(1);
+});