Add sync queue to Purgatory with enqueue_sync and has_pending_events

- Add sync_queue field to Purgatory struct for tracking identifiers that need
  background git data fetching
- Implement enqueue_sync() with debouncing - resets attempt_count and updates
  next_attempt when new events arrive for an identifier already in queue
- Add enqueue_sync_default() for user-submitted events (3 minute delay to wait
  for git push)
- Add enqueue_sync_immediate() for sync-triggered events (500ms delay for
  batching burst arrivals)
- Implement has_pending_events() to check if an identifier has state events
  or PR events in purgatory
- Add helper methods: sync_queue(), remove_from_sync_queue(), sync_queue_size()
- Add unit tests for debouncing behavior and pending event detection

0 files changed, 0 insertions, 0 deletions