feat: normalized external-agent status (#10 scoped) (v2.7.6)

Scoped half of boocode_code_review_v2 §1 #10 — publish the agent status
BooCoder already observes (the config-injection notify-hook is the documented
follow-on, clean-room from superset ELv2).

- agent_status_updated WS frame (working|blocked|idle|error), server+web parity.
- Published from the dispatcher's turn boundaries (warm-acp/opencode/sdk/pty:
  working at start, idle/error at end) + the permission flow (blocked/working).
  Best-effort, never breaks a turn.
- Clean-room normalizeAgentEvent helper (superset's vendor-event -> Start/blocked
  /Stop collapse, event names as facts) + 25 tests — reused by the follow-on.
- AgentComposerBar status dot (distinct from the WS-liveness dot), tracked per
  (chat,agent) by a useAgentStatus map in CoderPane.

Built by 2 parallel agents vs a pinned frame contract. Server 545 + coder 294
tests passing (25 new); web tsc + builds clean; ws-frames parity green. Clears
the actionable review backlog (#1/#3/#4/#6-#12). Builds on v2.7.5.

apps/web/src/hooks/useAgentStatus.ts

@@ -0,0 +1,62 @@
+import { useCallback, useMemo, useState } from 'react';
+
+// Normalized external-agent status (#10). Consumed from the
+// `agent_status_updated` WS frame the coder backend publishes:
+//   { type: 'agent_status_updated'; chat_id; agent; status; reason?; at }
+// BooCoder collapses ~30 vendor lifecycle events into these four buckets:
+//   working  — turn in flight
+//   blocked  — waiting on a permission / approval
+//   idle     — clean completion
+//   error    — crash / failure
+export type AgentStatus = 'working' | 'blocked' | 'idle' | 'error';
+
+export interface AgentStatusEntry {
+  status: AgentStatus;
+  reason?: string;
+  at: string;
+}
+
+const key = (chatId: string, agent: string): string => `${chatId}:${agent}`;
+
+// Per-(chat,agent) live status map. The dot reflects the latest frame for the
+// active agent in the current chat; entries are reset when the chat switches so
+// a stale "working"/"blocked" from a previous chat never leaks into the next.
+export function useAgentStatus() {
+  const [map, setMap] = useState<Record<string, AgentStatusEntry>>({});
+
+  const record = useCallback(
+    (chatId: string, agent: string, entry: AgentStatusEntry) => {
+      setMap((prev) => ({ ...prev, [key(chatId, agent)]: entry }));
+    },
+    [],
+  );
+
+  // Drop every entry for a chat (called on chat switch). No-op when nothing
+  // matches so it's safe to call unconditionally from an effect.
+  const reset = useCallback((chatId: string | undefined) => {
+    setMap((prev) => {
+      if (!chatId) return prev;
+      const prefix = `${chatId}:`;
+      let changed = false;
+      const next: Record<string, AgentStatusEntry> = {};
+      for (const [k, v] of Object.entries(prev)) {
+        if (k.startsWith(prefix)) {
+          changed = true;
+          continue;
+        }
+        next[k] = v;
+      }
+      return changed ? next : prev;
+    });
+  }, []);
+
+  const get = useCallback(
+    (chatId: string | undefined, agent: string | undefined): AgentStatusEntry | null => {
+      if (!chatId || !agent) return null;
+      return map[key(chatId, agent)] ?? null;
+    },
+    [map],
+  );
+
+  return useMemo(() => ({ record, reset, get }), [record, reset, get]);
+}

apps/web/src/hooks/useSessionStream.ts

@@ -189,6 +189,12 @@ function applyFrame(state: State, frame: WsFrame): State {
       // duplicating async work inside a synchronous reducer.
       return state;
     }
+    case 'agent_status_updated': {
+      // agent-status-normalize (#10): coder-only frame consumed by CoderPane's
+      // own WS handler, not BooChat's native message reducer. No-op here to keep
+      // TS exhaustiveness satisfied (native sessions never emit it).
+      return state;
+    }
   }
 }