- Add daemon=True class attribute (subclasses override to False)
- Add period=1 class attribute for wait interval
- Replace thread_stop boolean with _shutdown_event (threading.Event)
- Add wait() method for interruptible sleeps
- Update tests for new Event-based API
BREAKING: thread_stop boolean replaced with _shutdown_event.
Code checking thread.thread_stop directly must use thread._shutdown_event.is_set()