feat: transparent top bar with pill-styled panel items

GNOME 50 extension. Panel background fully transparent; each panel
button (clock, quick settings, indicators) gets a translucent rounded
pill with hover/active states. Clock's built-in inner highlight
suppressed to avoid double background.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

extension.js

@@ -0,0 +1,9 @@
+import {Extension} from 'resource:///org/gnome/shell/extensions/extension.js';
+
+// All styling lives in stylesheet.css, which GNOME Shell loads
+// automatically while the extension is enabled.
+export default class PanelPills extends Extension {
+    enable() {}
+
+    disable() {}
+}