Fix: Record refusals in admit_event and add persistence test

[ranjani-cse]

What breaks

Refusals in the autonomy governor leave no persistent trace. A defended night and an idle night look identical because there is no record of what was refused.

Steps to reproduce

1. Trigger an event that the governor refuses (e.g., an event from a self-actor or exceeding rate limit)
2. Check get_refusal_history() → returns empty or no record of the refusal

Test that fails before fix: proofs/test_refusal_persistence.py

The fix

Added _record_refusal method and updated admit_event to record refusals:

def _record_refusal(self, event, reason, verdict_type="refusal"):
    refusal_entry = {
        "timestamp": datetime.now(UTC).isoformat(),
        "event_id": getattr(event, "id", "unknown"),
        "source": getattr(event, "source", "unknown"),
        "actor": getattr(event, "actor", ""),
        "reason": reason,
        "type": verdict_type,
    }
    self.store.record_refusal(refusal_entry)