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/resources/styles/_osd.scss

@@ -0,0 +1,34 @@
+@use "sass:color";
+@use "colors";
+
+.osd {
+  background: rgba(colors.$bg-translucent-secondary, .6);
+  padding: 14px 14px;
+  border-radius: 24px;
+  min-width: 180px;
+
+  .icon {
+    margin-right: 10px;
+    -gtk-icon-size: 24px;
+  }
+
+  .level {
+    margin-top: -6px;
+
+    .text {
+      margin-bottom: 4px;
+      font-size: 14px;
+      font-weight: 600;
+    }
+
+    levelbar trough block {
+      border-radius: 4px;
+      background: colors.$bg-primary;
+
+      &.filled {
+        min-height: 10px;
+        background: colors.$bg-secondary;
+      }
+    }
+  }
+}