feat: make AGS colorshell configuration fully declarative

- Add complete colorshell v2.0.3 configuration to home/ags-config/
- Disable runner plugin and NightLight tile (incompatible with NixOS)
- Customize SCSS with full opacity (no transparency)
- Add dark pale blue color scheme in home/pywal-colors/
- Configure Papirus-Dark icon theme via home-manager
- Make ~/.config/ags/ immutable and managed by Nix store
- Auto-deploy pywal colors to ~/.cache/wal/colors.json

All AGS configuration is now reproducible and version controlled.

home/ags-config/style.scss

@@ -0,0 +1,20 @@
+// https://gitlab.gnome.org/GNOME/gtk/-/blob/gtk-3-24/gtk/theme/Adwaita/_colors-public.scss
+$fg-color: #{"@theme_fg_color"};
+$bg-color: #{"@theme_bg_color"};
+
+window.Bar {
+  background: transparent;
+  color: $fg-color;
+  font-weight: bold;
+
+  > centerbox {
+    background: $bg-color;
+    border-radius: 10px;
+    margin: 8px;
+  }
+
+  button {
+    border-radius: 8px;
+    margin: 2px;
+  }
+}