Adds comprehensive unit tests for `js/utils/videoTimestamps.js` using the native Node.js test runner.
- Covers `getVideoRootIdentifier`, `applyRootTimestampToVideosMap`, and `syncActiveVideoRootTimestamp`.
- Verifies handling of invalid inputs, edge cases (e.g., missing IDs, type mismatches), and state updates.
- Ensures robust timestamp synchronization logic.
This addresses the testing gap identified in `js/utils/videoTimestamps.js`.
Co-authored-by: PR0M3TH3AN <[email protected]>
