fix: memory leak cleanup, lifecycle ack protocol, driver-managed slot notifications

Memory leaks:
- Add clearSlotTracking/clearAllTracking exports to monitor.ts
- Add clearCrashHistory/clearAllCrashHistory exports to recovery.ts
- Wire cleanup into end_session and delete_session handlers
- Clean completionRestartHistory, transitionedToWorking, lastTokenTotals,
  crashHistory on session end

Lifecycle acknowledgment:
- Broker signal_done, submit_feedback, approve now return notified_count
- Base adapter lifecycle handlers trigger immediate self-poll after
  broker call (picks up any instant responses without waiting for
  next poll cycle)

Driver-managed slot notifications:
- Broker signal_done now notifies driver-managed Codex slots (no peer_id)
  using __slot_N__ virtual target — messages stored with to_slot_id and
  picked up by pollBySlot
- Same fix for submit_feedback and approve message insertion