fix(channel): add describeAccount so health-monitor sees real configured

openclaw's `channelManager.getRuntimeSnapshot()` — called every minute
by the channel-health-monitor — runs accounts through
`applyDescribedAccountFields(next, plugin.config.describeAccount?.(...))`.
When the callback is missing it defaults `configured: true`. Fabric
never defined it, so every health-monitor cycle:

  snapshot = { enabled: true, configured: true, running: false }

For fabric's synthetic 'default' account (returned by
`listFabricAccountIds` when `channels.fabric.accounts` is empty —
the prod shape, where per-agent api-keys live in
`~/.openclaw/fabric-identity.json` and the channel framework never
runs `startAccount` so `running` stays false):

  isManagedAccount({enabled:true, configured:true}) === true
  -> not-running -> 'stopped' -> restart every ~10 min, logging
  '[fabric:default] health-monitor: restarting (reason: stopped)'

The restart is a no-op (fabric's `gateway.startAccount` is absent so
`startChannelInternal` returns early), but the log is loud and
operators chasing real outages keep wasting time on it.

Mirror `isConfigured` from describeAccount so the snapshot
truthfully reports configured:false for any account without a
fabricApiKey. The fabric plugin still self-manages real agents via
`gateway_start` -> `FabricInbound.start()`; the framework just no
longer thinks 'default' is something it should restart.

Verified in sim (this patch alone, no debug instrumentation):
- gateway up 8+ minutes, 0 restart events
- pre-patch sim with same config restarted at 5min mark
- evaluateChannelHealth snapshot for both 'default' and 'recruiter'
  accountId reads configured:false (instrumented with temporary
  console.log in channel-health-policy, since reverted)

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

src/channel.ts

@@ -153,6 +153,19 @@ export const fabricChannelPlugin = createChatChannelPlugin<ResolvedFabricAccount
       resolveAccount: (cfg, accountId) => resolveFabricAccount(cfg as never, accountId),
       defaultAccountId: (cfg) => resolveDefaultFabricAccountId(cfg as never),
       isConfigured: (account: ResolvedFabricAccount) => Boolean(account.fabricApiKey),
+      // openclaw's channelManager.getRuntimeSnapshot() — called every minute
+      // by the channel-health-monitor — defaults `configured: true` when the
+      // plugin doesn't expose describeAccount (see applyDescribedAccountFields
+      // in server-channels). Without this, fabric's synthetic 'default'
+      // account (returned by listFabricAccountIds when channels.fabric.accounts
+      // is empty — the prod shape) gets snapshot {enabled:true, configured:true,
+      // running:false} → isManagedAccount=true → not-running → restart loop
+      // every ~10 min, logging `[fabric:default] health-monitor: restarting`.
+      // Mirror isConfigured here so the snapshot truthfully reports false for
+      // any account without a fabricApiKey.
+      describeAccount: (account: ResolvedFabricAccount) => ({
+        configured: Boolean(account.fabricApiKey),
+      }),
     },
     // Minimal setup adapter: Fabric is configured directly under
     // channels.fabric.* (no interactive wizard). applyAccountConfig is the