fix(studio): 修复流式返回时空间引用角标渲染错乱

Streamdown 的 parseIncompleteMarkdown 会把流式途中未闭合的 [[cite:N
当作未完成链接改写成 [[cite:N](streamdown:incomplete-link)，导致
rehypeCitations 匹配失败、引用闪成坏链接。送入渲染前剥除未完成的引用
标记，待 ]] 到齐再由 rehype 渲染为上标。

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend-web/src/components/workspace/messages/message-list-item.tsx

@@ -358,6 +358,20 @@ function MessageImage({
   );
 }
 
+// While a notebook citation marker is still streaming in (e.g. "[[cite:64" or
+// "[[cite:101]"), Streamdown's parseIncompleteMarkdown treats the trailing
+// unclosed "[" as an incomplete link and rewrites it to
+// "[[cite:64](streamdown:incomplete-link)", which the rehypeCitations regex can
+// no longer match — so the citation flickers as a broken link mid-stream. We
+// strip the half-arrived marker so it stays hidden until the closing "]]"
+// arrives, at which point rehypeCitations renders it. A complete
+// "[[cite:101]]" has no trailing incomplete marker, so this is a no-op.
+const INCOMPLETE_CITE_TAIL = /\[\[(?:c(?:i(?:t(?:e(?::\d*\]?)?)?)?)?)?$/;
+
+function stripIncompleteCitationMarker(content: string): string {
+  return content.replace(INCOMPLETE_CITE_TAIL, '');
+}
+
 function MessageContent_({
   className,
   message,
@@ -460,7 +474,8 @@ function MessageContent_({
         ? stripArtifactTag(stripUploadedFilesTag(rawContent))
         : '';
     }
-    return applyInlineCitations(rawContent ?? '', displaySources);
+    const withCitations = applyInlineCitations(rawContent ?? '', displaySources);
+    return stripIncompleteCitationMarker(withCitations);
   }, [rawContent, isHuman, displaySources]);
   const parsedHumanContent = useMemo(
     () =>