- build the video save-dialog filter from VIDEO_EXTENSIONS (_VIDEO_FILE_FILTER)
instead of a hardcoded "Videos (*.mp4 *.mkv)" — the last filter that still
drifted from the canonical set
- remove the now-dead file_types list (unused in both the fork and upstream;
the PySide6 dialogs use the QFileDialog filter strings) and drop it from the
centralization comment