Pilot state machine

Prepared → Activating → ProcessStarting → WaitingForRuntimeCheck → RolledBack

Failures are persisted as Failed. A new run is blocked by an active session; a completed RolledBack session permits a new run. pilot rollback restores state from its persisted activation snapshot and is repeatable.

The current session schema persists the terminal state. It does not yet persist a transition-history array; evidence must not infer intermediate transitions after the fact.