Add patrol instance tracking to witness manager:
- Add PatrolInstanceID to WitnessHandoffState for tracking
- Add ArmID to WorkerState for per-polecat arm tracking
- Add ensurePatrolInstance() method that:
- Checks if patrol instance already exists (from previous session)
- Creates new patrol instance if needed
- Persists instance ID in handoff state
This enables the molecule-based tracking ledger pattern where the
Go-based witness creates beads issues to track its patrol state.
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Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>