Redesign comment replies as glass bubbles

- Top-level comments keep their existing layout (avatar, name,
  timestamp, text, action bar)
- Replies now render in a rounded glass bubble with subtle
  background and border, chat-message style (flat top-left
  corner, rounded on the other three)
- Smaller avatars and more compact action buttons for replies
- Reply form pulled outside the comment layout for cleaner
  nesting at all depths
- Better spacing between comment threads

Co-authored-by: Cursor <cursoragent@cursor.com>

src/components/ContentDetailModal.vue

@@ -177,7 +177,7 @@
                 <div class="text-white/40 text-sm">No comments yet. Be the first!</div>
               </div>
 
-              <!-- Threaded comments (bubble layout) -->
+              <!-- Threaded comments -->
               <div v-else class="space-y-2">
                 <template v-for="node in commentTree" :key="node.event.id">
                   <CommentNode