feat(ui): display livePartial / transcript_delta in ChatBubble as 'Hearing:' indicator

- REST STT now sends delta (full text) so UI lights up immediately with what was heard.
- Works as 'live' for the final transcript (true partials would stream words if Realtime was available).
- Per PLAN item 3.

frontend/src/components/ChatBubble.tsx

@@ -11,9 +11,10 @@ interface Props {
   messages: Message[];
   isKiraSpeaking: boolean;
   userName?: string;
+  livePartial?: string;
 }
 
-export default function ChatBubble({ messages, isKiraSpeaking }: Props) {
+export default function ChatBubble({ messages, isKiraSpeaking, livePartial }: Props) {
   const bottomRef = useRef<HTMLDivElement>(null);
 
   useEffect(() => {
@@ -27,6 +28,15 @@ export default function ChatBubble({ messages, isKiraSpeaking }: Props) {
         <span className={`w-2 h-2 rounded-full ${isKiraSpeaking ? 'bg-kira-pink animate-pulse' : 'bg-kira-mint'}`} />
       </h3>
 
+      {livePartial && (
+        <div className="mb-2 px-3 py-1.5 bg-kira-lav/20 text-kira-plum/70 text-xs rounded-xl flex items-center gap-2">
+          <span>👂</span>
+          <span className="font-medium">Hearing:</span>
+          <span className="truncate">{livePartial}</span>
+          <span className="animate-pulse">...</span>
+        </div>
+      )}
+
       <div className="flex-1 overflow-y-auto space-y-2 scrollbar-thin pr-1">
         {messages.length === 0 && (
           <div className="text-xs text-kira-plum/30 text-center py-6">