fix: prevent page scroll when transcript updates

Scroll only within transcript container, not the entire page.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/components/configurator/VoiceAgent.tsx

@@ -64,9 +64,12 @@ export default function VoiceAgent({ locale, onComplete }: VoiceAgentProps) {
 
   const transcriptEndRef = useRef<HTMLDivElement>(null);
 
-  // Auto-scroll transcript
+  // Auto-scroll transcript within its container only
   useEffect(() => {
-    transcriptEndRef.current?.scrollIntoView({ behavior: 'smooth' });
+    const el = transcriptEndRef.current;
+    if (el?.parentElement) {
+      el.parentElement.scrollTop = el.parentElement.scrollHeight;
+    }
   }, [transcript]);
 
   // Handle completion