phsl / new-api

When using the "reset messages simultaneously" option during config import,
the conversation messages in the chat interface were not being properly reset,
while normal conversation resets worked correctly.

**Changes:**
- Modified `handleConfigReset` in `usePlaygroundState.js` to clear messages
  before setting default examples
- Added asynchronous message update to force Chat component re-render
- Ensures immediate UI refresh when resetting imported conversation data

**Root Cause:**
The direct assignment to DEFAULT_MESSAGES didn't trigger a complete
component refresh, causing the chat interface to display stale data.

**Solution:**
```javascript
// Before
setMessage(DEFAULT_MESSAGES);

// After
setMessage([]);
setTimeout(() => {
  setMessage(DEFAULT_MESSAGES);
}, 0);
```

This two-step approach forces the Chat component to unmount and remount
with fresh data, resolving the display inconsistency.