fix: check dest_path when filtering watchdog reload events

[dmamelin]

Fixes #871

Editors that save atomically (temp file + os.replace/rename — e.g. Blueprint Studio) surface as a FileMovedEvent where src_path is the temp file name and dest_path is the real script path. check_event only checked src_path, so these saves were silently ignored and the reload never fired.

Now both src_path and dest_path are checked against the allowed suffixes.

Testing

check_event currently has no dedicated tests - the watchdog wiring itself is mocked out everywhere it's touched. Given the fix is a one-line, low-risk check (also inspect dest_path for moved events), I kept this PR minimal rather than doing an unrelated refactor to make check_event independently testable. Happy to extract it to a module-level function and add unit tests if you'd like coverage for this specific case.

[craigbarratt]

Thank for the PR - looks good.