closes#15
- NodeStore: SQLite persistence for known agent nodes
(~/.local/share/circuitforge/cf-orch-nodes.db)
- upsert on every register(); prune_stale() for 30-day cleanup
- survives coordinator restarts — data readable by next process
- AgentSupervisor.restore_from_store(): reload known nodes on startup,
mark all offline; heartbeat loop brings back any that respond
- AgentSupervisor.register(): persists to NodeStore on every call
- cli.py coordinator: NodeStore wired in; restore_from_store() called
before uvicorn starts
- cli.py agent: one-shot registration replaced with persistent reconnect
loop (daemon thread, 30 s interval) — coordinator restart → nodes
reappear within one cycle with no manual intervention on agent hosts
- 16 new tests: NodeStore (8) + AgentSupervisor watchdog (8)