feat(agent-office): notification broadcast + telegram tracking + activity feed API

- Add WebSocket notification messages for task_assigned/task_completed
- Structure telegram send_message return value with ok/message_id
- Track telegram delivery status in task result_data
- Add test_telegram command to stock agent
- Add GET /api/agent-office/activity unified feed endpoint

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

agent-office/app/main.py

@@ -4,7 +4,7 @@ from fastapi import FastAPI, HTTPException, WebSocket, WebSocketDisconnect
 from fastapi.middleware.cors import CORSMiddleware
 
 from .config import CORS_ALLOW_ORIGINS
-from .db import init_db, get_all_agents, get_agent_config, update_agent_config, get_agent_tasks, get_pending_approvals, get_task, get_logs
+from .db import init_db, get_all_agents, get_agent_config, update_agent_config, get_agent_tasks, get_pending_approvals, get_task, get_logs, get_activity_feed
 from .models import CommandRequest, ApprovalRequest, AgentConfigUpdate
 from .websocket_manager import ws_manager
 from .agents import init_agents, get_agent, get_all_agent_states, AGENT_REGISTRY
@@ -150,3 +150,7 @@ async def telegram_webhook(data: dict):
 @app.get("/api/agent-office/states")
 def all_states():
     return {"agents": get_all_agent_states()}
+
+@app.get("/api/agent-office/activity")
+def activity_feed(limit: int = 50, offset: int = 0):
+    return get_activity_feed(limit, offset)