fix(codeBlock): 修复代码块抖动的问题

frontend/src/components/workspace/messages/message-group.tsx

@@ -263,8 +263,9 @@ function ToolCall({
     language?: BundledLanguage;
     expanded?: boolean;
   }) => {
-    // Always start collapsed in thinking blocks; user must explicitly expand.
-    const shouldShowCodeBlock = expanded;
+    // During streaming, never render code block content in thinking area.
+    // Code is only available for expand/collapse after streaming is complete.
+    const shouldShowCodeBlock = !isLoading && expanded;
 
     return (
       <div className="space-y-1">
@@ -462,8 +463,10 @@ function ToolCall({
           <Button
             className="h-7 px-3 text-xs"
             variant="ghost"
+            disabled={isLoading}
             onClick={(event) => {
               event.stopPropagation();
+              if (isLoading) return;
               setIsCommandExpanded((prev) => !prev);
             }}
           >