fix(reload): filter filesystem events before queueing

[zmylol]

Filesystem open and close events were queued by watchdog and only discarded later by FileWatcher.dispatch(). When event dispatch was blocked, read-only file access could keep adding unnecessary events to the queue.

Configure Observer.schedule() to accept only file creation, modification, deletion, and movement events. Closing events were already ignored by FileWatcher, so excluding them before queueing preserves existing reload behavior.

Require watchdog >= 4.0.2 because that version adds event_filter support to macOS's FSEventsObserver.

Validation:

• Full test suite on Windows: 383 passed.
• Linux regression tests: 14 passed with watchdog 6.0.0; 12 passed and 2 expected skips with 4.0.2.
• Native Linux checks verified blocked dispatch, 500 read-only accesses, recursive watching, and atomic file replacement.
• All checks passed for the changed files.

Fixes #684