Refresh cheatsheet.md with tested DMS keybindings and actual working
setup (e.g. SUPER+T for terminal, DMS spotlight, lxpolkit instead of
broken hyprpolkitagent). Update plan.md to replace hyprpolkitagent
with lxpolkit (Qt 6 ABI issue). Add detailed phase 1-3 progress notes
including lxpolkit workaround, hyprland.conf + hyprpaper verification,
and dotfiles stow integration.