Replace swaylock with gtklock; centralise theme palette

- Replace swaylock with gtklock (username + password form lockscreen)
- Add gtklock/config.ini and gtklock/style.css (Tomorrow Night theme)
- Update niri keybindings and swayidle to invoke gtklock -d
- Update packages.txt: swaylock -> gtklock
- Update install.sh: add AUR helper detection (yay/paru), symlink gtklock configs
- Add theme/colors.css (CSS custom properties) and theme/colors.json
- Update waybar/style.css, wofi/style.css, gtklock/style.css to import shared palette
- Update README.md with project summary and component table
- Add ARCHITECTURE.md and CLAUDE.md

README.md

@@ -1,5 +1,24 @@
 # Dotfiles (Niri + Wayland)
 
+A personal Wayland desktop configuration centered around the **Niri** tiling compositor.
+
+| Area | Tool |
+|---|---|
+| Compositor | niri |
+| Bar | waybar |
+| Terminal | alacritty |
+| Shell | fish + starship |
+| Launcher | wofi |
+| Notifications | mako |
+| Lockscreen | gtklock |
+| Login/greeter | greetd + regreet |
+| Wallpaper | swww |
+| Screenshots | grim + slurp |
+| Clipboard | cliphist |
+| Theme | Tomorrow Night (GTK: Materia-dark, icons: Papirus) |
+
+Everything is symlinked into `~/.config` via `install.sh`, with packages listed in `packages.txt`.
+
 ## Setup
 
 ```bash