Locks the ordered rungs without real compositors: portal first where a
backend implements it (GNOME), direct typing first on niri with IBus
excluded and no portal selected, deny demoting to direct typing with the
full dictation kept, terminal probe choosing Ctrl+Shift+V, held modifiers
delaying the XWayland paste, and clipboard manual paste as last resort.
USER_GUIDE states the niri first run (no prompt, typing goes direct,
never pin portal there) and the GNOME/KDE grant, persistence and deny
fallback under the renamed backend setting and override names.
Refs #31
