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/db.py

@@ -259,3 +259,64 @@ def mark_telegram_responded(callback_id: str, action: str) -> None:
             "UPDATE telegram_state SET responded=1, action=? WHERE callback_id=?",
             (action, callback_id),
         )
+
+
+def get_activity_feed(limit: int = 50, offset: int = 0) -> dict:
+    with _conn() as conn:
+        total_row = conn.execute("""
+            SELECT (SELECT COUNT(*) FROM agent_tasks) + (SELECT COUNT(*) FROM agent_logs) AS total
+        """).fetchone()
+        total = total_row["total"] if total_row else 0
+
+        rows = conn.execute("""
+            SELECT 'task' AS type, agent_id, id AS task_id, task_type,
+                   status, NULL AS level,
+                   COALESCE(
+                       json_extract(result_data, '$.summary'),
+                       task_type
+                   ) AS message,
+                   created_at, completed_at,
+                   result_data
+            FROM agent_tasks
+            UNION ALL
+            SELECT 'log' AS type, agent_id, task_id, NULL AS task_type,
+                   NULL AS status, level,
+                   message,
+                   created_at, NULL AS completed_at,
+                   NULL AS result_data
+            FROM agent_logs
+            ORDER BY created_at DESC
+            LIMIT ? OFFSET ?
+        """, (limit, offset)).fetchall()
+
+    items = []
+    for r in rows:
+        item = {
+            "type": r["type"],
+            "agent_id": r["agent_id"],
+            "task_id": r["task_id"],
+            "message": r["message"],
+            "created_at": r["created_at"],
+        }
+        if r["type"] == "task":
+            item["task_type"] = r["task_type"]
+            item["status"] = r["status"]
+            item["completed_at"] = r["completed_at"]
+            if r["created_at"] and r["completed_at"]:
+                try:
+                    from datetime import datetime
+                    start = datetime.fromisoformat(r["created_at"].replace("Z", "+00:00"))
+                    end = datetime.fromisoformat(r["completed_at"].replace("Z", "+00:00"))
+                    item["duration_seconds"] = round((end - start).total_seconds())
+                except Exception:
+                    item["duration_seconds"] = None
+            else:
+                item["duration_seconds"] = None
+            result_data = json.loads(r["result_data"]) if r["result_data"] else None
+            if result_data and "telegram_sent" in result_data:
+                item["telegram_sent"] = result_data["telegram_sent"]
+        else:
+            item["level"] = r["level"]
+        items.append(item)
+
+    return {"items": items, "total": total}