A file named portable.txt beside the executable keeps settings, logs,
the GPU start-up record and crash recovery in a DesignCraftData folder
next to it instead of the per-user folders, as PhotoCraft and FilmCraft
do. A folder of that name is not a marker. DESIGNCRAFT_CONFIG_DIR still
wins, empty or not. The Windows portable zip now ships portable.txt;
the MSI and the macOS app bundle don't, so nothing changes there.