- NodeRegistryService: in-memory live node registry with rich EventBus
  - emit() delivers all execution events to per-node and per-user subscribers
  - EVENT_TYPES: 20 structured event types (task_start, sync_drift, retry, etc.)
- AgentNode DB model: persists node registrations + invite_token + last_status
- DB migration: auto-creates agent_nodes table + adds new columns
- REST API (/nodes):
  GET  /nodes                   - list all user's nodes (live+DB merged)
  GET  /nodes/{node_id}         - full live status
  GET  /nodes/{node_id}/status  - quick online/offline probe
  POST /nodes/{node_id}/dispatch - dispatch shell/browser task to a node
- WebSocket API:
  WS /nodes/{node_id}/stream    - single-node live execution stream
  WS /nodes/stream/all          - multi-node global bus (split-pane UI ready)