🐛 fix(playground): set Chat error text color to white to match Semi UI

- Update error-state rendering to use white text in the playground chat
- Remove Typography.Text `type="danger"` and the red background for consistency with official behavior
- Preserve layout and other message states (loading/success/system) unchanged
- No linter issues introduced

Files touched:
- web/src/components/playground/MessageContent.jsx

web/src/components/playground/MessageContent.jsx

@@ -71,8 +71,8 @@ const MessageContent = ({
     }
 
     return (
-      <div className={`${className} flex items-center p-4 bg-red-50 rounded-xl`}>
-        <Typography.Text type="danger" className="text-sm">
+      <div className={`${className}`}>
+        <Typography.Text className="text-white">
           {errorText}
         </Typography.Text>
       </div>