v2.0.0b22

feat(scheduler): add adaptive file polling with FileWatcher

Add a new polling module that provides hybrid file watching:
- FileWatcher combines watchdog with adaptive polling (0.5s to 30s)
- When watchdog fires, polling interval resets to minimum
- When files are idle, polling interval gradually increases
- Provides reliable change detection as fallback when watchdog misses events

Integrate FileWatcher into EventReader for more reactive file monitoring.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>