feat: add right-click object inspection for 3D objects

Right-clicking any inspectable 3D mesh or sprite now shows a
holographic tooltip with the object's name and description.

Tagged objects: glass platform, platform rim, sovereignty meter,
sovereignty score sprite, agent panels, and commit banners.
The contextmenu handler uses THREE.Raycaster against all scene
children and surfaces the first hit with userData.inspectName.
Tooltip dismisses on click or Escape.

Fixes #141

index.html

@@ -48,6 +48,11 @@
 
   <div id="sovereignty-msg">⚡ SOVEREIGNTY ⚡</div>
 
+  <div id="inspect-tooltip">
+    <div id="inspect-name"></div>
+    <div id="inspect-desc"></div>
+  </div>
+
   <script type="module" src="app.js"></script>
 <div id="loading" style="position: fixed; top: 0; left: 0; right: 0; height: 4px; background: #222; z-index: 1000;">
   <div id="loading-bar" style="height: 100%; background: var(--color-accent); width: 0;"></div>