v0.5.3 — fix .desktop Test action under launchers

Fixed

• .desktop "Preview an effect inline" action wrapped in
  alacritty -e ... so it works when invoked from a desktop
  launcher (Fuzzel, Anyrun, GNOME Activities, etc.). The
  underlying niri-screensaver-ctl test needs a TTY for tte
  to render; without the wrapper, launcher invocations silently
  no-op. CLI use was always fine. Alacritty is already a hard
  runtime dep, so no new dependency.