修复无语言代码围栏样式

将包含换行的无语言围栏内容识别为代码块。

新增回归测试，确保其使用块级代码样式而非内联样式。

apps/ai-game-creator-shell/src/components/ChatMarkdownMessage/index.tsx

@@ -80,7 +80,9 @@ const markdownComponents: Components = {
     </pre>
   ),
   code: ({ className, children, node: _node, ...props }) => {
-    const isBlock = Boolean(className?.includes('language-'));
+    const isBlock =
+      Boolean(className?.includes('language-')) ||
+      String(children).includes('\n');
     return isBlock ? (
       <code {...props} className="font-mono whitespace-pre">
         {children}

apps/ai-game-creator-shell/tests/ChatMarkdownMessage.test.tsx

@@ -34,6 +34,19 @@ describe('ChatMarkdownMessage', () => {
     ).toBeNull();
   });
 
+  it('无语言标记的多行围栏代码仍使用代码块样式', () => {
+    const { container } = render(
+      <ChatMarkdownMessage
+        role="assistant"
+        text={'```\nconst answer = 42;\nreturn answer;\n```'}
+      />,
+    );
+
+    const code = container.querySelector('pre code');
+    expect(code?.className).toContain('whitespace-pre');
+    expect(code?.className).not.toContain('rounded');
+  });
+
   it('保留流式 assistant 文本并标记 streaming 状态', () => {
     const { container } = render(
       <ChatMarkdownMessage