fix: Remove delay for instant reasoning block collapse

- Remove 500ms setTimeout delay when reasoning finishes
- Reasoning block now collapses immediately when response starts
- Creates smoother transition from thinking to response phase
- Eliminates jarring delay between reasoning end and collapse

The reasoning block now collapses instantly as soon as the model
starts generating the actual response, providing better UX flow.

examples/chat-ui/src/components/ReasoningBlock.tsx

@@ -15,14 +15,10 @@ const ReasoningBlock: React.FC<ReasoningBlockProps> = ({
 }) => {
     const [isExpanded, setIsExpanded] = useState(isStreaming); // Start expanded when streaming
     
-    // Auto-collapse when streaming finishes
+    // Auto-collapse instantly when streaming finishes
     useEffect(() => {
         if (!isStreaming && startTime && endTime) {
-            // Add a small delay before collapsing so user can see completion
-            const timer = setTimeout(() => {
-                setIsExpanded(false);
-            }, 500);
-            return () => clearTimeout(timer);
+            setIsExpanded(false);
         }
     }, [isStreaming, startTime, endTime]);