Implement Phase 1: LangGraph backend MVP

Sets up the full backend foundation for CouncilOS:

- CouncilState TypedDict with all required fields and LangGraph reducers
- Three agent nodes: master_agent (drafts), critic_agent (scores + routes),
  writer_agent (final polish)
- LangGraph graph with cyclic rework loop: Master → Critic → (score < 8:
  back to Master | score ≥ 8: Writer → END)
- Safety valve: MAX_ITERATIONS=5 prevents infinite loops
- FastAPI app with REST endpoints (POST /api/councils/run, GET /api/councils/run/{id})
  and WebSocket endpoint (/ws/council/{run_id}) for real-time agent status events
- In-memory RunStore for Phase 1 (PostgreSQL-backed in Phase 3)
- pytest test suite: state, routing logic, critic parser, agent nodes, API endpoints
- .env.example, .gitignore, docker-compose.yml, Dockerfile

https://claude.ai/code/session_01RfMpt3TbMjZEtK3CAyP5iQ

backend/api/websocket.py

@@ -0,0 +1,128 @@
+"""
+WebSocket endpoint for real-time agent status updates.
+
+Clients connect to /ws/council/{run_id} and receive JSON events whenever
+an agent node becomes active. This powers the live diagram pulsing in the frontend.
+
+Event format:
+    {"event": "node_start", "run_id": "...", "node": "master_agent", "iteration": 2}
+    {"event": "node_complete", "run_id": "...", "node": "critic_agent", "score": 6.5}
+    {"event": "run_complete", "run_id": "...", "final_draft": "..."}
+    {"event": "run_failed", "run_id": "...", "error": "..."}
+"""
+
+import asyncio
+import json
+from fastapi import APIRouter, WebSocket, WebSocketDisconnect
+
+from api.run_store import run_store
+
+
+ws_router = APIRouter()
+
+# Active WebSocket connections keyed by run_id
+_connections: dict[str, list[WebSocket]] = {}
+
+
+async def broadcast_event(run_id: str, event: dict) -> None:
+    """
+    Send an event to all WebSocket clients subscribed to a run_id.
+
+    Args:
+        run_id: The council run identifier.
+        event:  The event dict to serialize and broadcast.
+    """
+    clients = _connections.get(run_id, [])
+    disconnected = []
+
+    for ws in clients:
+        try:
+            await ws.send_text(json.dumps(event))
+        except Exception:  # noqa: BLE001
+            disconnected.append(ws)
+
+    # Clean up dead connections
+    for ws in disconnected:
+        clients.remove(ws)
+
+
+@ws_router.websocket("/ws/council/{run_id}")
+async def council_websocket(websocket: WebSocket, run_id: str):
+    """
+    WebSocket endpoint for live council run updates.
+
+    On connect: sends the current run status immediately.
+    While running: polls the run store and pushes status changes.
+    On complete/failed: sends a final event and closes the connection.
+    """
+    await websocket.accept()
+
+    # Register this client
+    if run_id not in _connections:
+        _connections[run_id] = []
+    _connections[run_id].append(websocket)
+
+    try:
+        # Send current state immediately on connect
+        run = run_store.get(run_id)
+        if run is None:
+            await websocket.send_text(
+                json.dumps({"event": "error", "message": f"Run '{run_id}' not found."})
+            )
+            return
+
+        await websocket.send_text(
+            json.dumps({"event": "connected", "run_id": run_id, "status": run["status"]})
+        )
+
+        # Poll for status changes and push updates
+        last_node = None
+        while True:
+            run = run_store.get(run_id)
+            if run is None:
+                break
+
+            current_node = run.get("active_node")
+            if current_node and current_node != last_node:
+                await websocket.send_text(
+                    json.dumps({
+                        "event": "node_active",
+                        "run_id": run_id,
+                        "node": current_node,
+                        "iteration": run.get("iteration_count"),
+                    })
+                )
+                last_node = current_node
+
+            if run["status"] == "completed":
+                await websocket.send_text(
+                    json.dumps({
+                        "event": "run_complete",
+                        "run_id": run_id,
+                        "final_draft": run.get("final_draft"),
+                        "critic_score": run.get("critic_score"),
+                        "iteration_count": run.get("iteration_count"),
+                    })
+                )
+                break
+
+            if run["status"] == "failed":
+                await websocket.send_text(
+                    json.dumps({
+                        "event": "run_failed",
+                        "run_id": run_id,
+                        "error": run.get("error"),
+                    })
+                )
+                break
+
+            await asyncio.sleep(0.5)  # 500ms polling interval
+
+    except WebSocketDisconnect:
+        pass
+    finally:
+        if run_id in _connections:
+            try:
+                _connections[run_id].remove(websocket)
+            except ValueError:
+                pass