feat(hf-plugin): expose globalThis.__hfAgentStatus.get(agentId)

Cross-plugin agent-status accessor for use by Fabric.OpenclawPlugin's
presence-sync loop (and any future plugin needing 'is agent X busy
right now'). Backed by CalendarBridgeClient.getAgentStatus() with a
30s in-memory TTL cache to avoid hammering the HF backend.

Returns one of 'idle' | 'on_call' | 'busy' | 'exhausted' | 'offline'
or undefined when the agent isn't known to HF. Cache miss + bridge
failure returns the last cached value (stale-data better than no
data for delivery-decision use cases).

Part of DIALECTIC-V2 Phase 1 (Fabric announce channel + busy-discard).
See /home/hzhang/arch/DIALECTIC-V2-DESIGN.md sections 7+8.

plugin/index.ts

@@ -396,6 +396,36 @@ function register(api: PluginAPI): void {
         }
       }
 
+      // Cross-plugin exposure: agent status lookup for other plugins
+      // (currently Fabric.OpenclawPlugin uses this to skip delivering
+      // `announce` channel messages to busy agents — see DIALECTIC-V2
+      // design doc, Phase 1). Backed by calendarBridge.getAgentStatus
+      // with a small TTL cache to avoid hammering the HF backend.
+      type HfStatus = 'idle' | 'on_call' | 'busy' | 'exhausted' | 'offline';
+      const HF_STATUS_CACHE_TTL_MS = 30_000;
+      const hfStatusCache = new Map<string, { status: HfStatus; at: number }>();
+      const _G = globalThis as Record<string, unknown>;
+      _G['__hfAgentStatus'] = {
+        async get(agentId: string): Promise<HfStatus | undefined> {
+          if (!agentId) return undefined;
+          const cached = hfStatusCache.get(agentId);
+          if (cached && Date.now() - cached.at < HF_STATUS_CACHE_TTL_MS) {
+            return cached.status;
+          }
+          try {
+            const status = await calendarBridge.getAgentStatus(agentId);
+            if (status) {
+              const typed = status as HfStatus;
+              hfStatusCache.set(agentId, { status: typed, at: Date.now() });
+              return typed;
+            }
+          } catch {
+            /* fall through to cached-or-undefined */
+          }
+          return cached?.status;
+        },
+      };
+
       // Track wakes already dispatched for a slot in the current sync
       // window — the simplified inline scheduler does not PATCH slot
       // status server-side, so without dedupe the check loop re-wakes