* Add WebSocket gateway and control plane endpoint
Adds bidirectional WebSocket transport to the web gateway alongside
the existing SSE stream. Clients can send messages, approvals, and
pings over a single persistent connection at /api/chat/ws.
- Enable axum `ws` feature for built-in WebSocket support
- Add WsClientMessage/WsServerMessage types with tagged JSON protocol
- Add subscribe_raw() to SseManager for non-SSE consumers
- Create ws.rs with connection handler (split sender/receiver tasks)
- Add WsConnectionTracker for active connection counting
- Add /api/gateway/status control plane endpoint (SSE + WS counts)
- 35 new tests covering message types, broadcast, and handler logic
https://claude.ai/code/session_01KEaLN6Xq2j5EeV3SGHQT6b
* Add e2e WebSocket gateway integration tests
- Add tokio-tungstenite dev-dependency for WebSocket client in tests
- Update start_server to return actual bound SocketAddr (enables port 0)
- Add 10 e2e tests covering full HTTP upgrade → WebSocket → message flow:
ping/pong, message routing to agent, broadcast event delivery,
connection tracking, invalid message handling, auth rejection,
gateway status endpoint, and multi-event sequencing
https://claude.ai/code/session_01KEaLN6Xq2j5EeV3SGHQT6b
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Co-authored-by: Claude <[email protected]>
