Introduces the maestro-protocol crate (NAP-211): the shared serde
types that the daemon, registry, and clients all serialize across
WebSocket boundaries. Covers:
- Session, SessionStatus
- CreateSessionRequest with optional WorktreeSpec
- RpcResult<T> reply envelope
- DaemonOutbound (Hello, snapshot, add/remove/update,
Heartbeat, request results)
- DaemonInbound (Ack, Error, CreateSession, KillSession)
- ClientControl text frames (Resize, Ping, Pong, Error)
Schema mirrors the wire-protocol tables in the design spec. Unit
tests round-trip every variant and assert tag/discriminator
stability so future renames break loudly.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
