feat(frontend): unify citation logic and prevent half-finished citations

- Add SafeCitationContent as single component for citation-aware body:
  useParsedCitations + shouldShowCitationLoading; show loading until
  citations complete, then render body with createCitationMarkdownComponents.
  Supports optional remarkPlugins, rehypePlugins, isHuman, img.

- Refactor MessageListItem: assistant message body now uses
  SafeCitationContent only; remove duplicate useParsedCitations,
  shouldShowCitationLoading, createCitationMarkdownComponents and
  CitationsLoadingIndicator logic. Human messages keep plain
  AIElementMessageResponse (no citation parsing).

- Use SafeCitationContent for clarification, present-files (message-list),
  thinking steps and write_file loading (message-group), subtask result
  (subtask-card). Artifact markdown preview keeps same guard
  (shouldShowCitationLoading) with ArtifactFilePreview.

- Unify loading condition: shouldShowCitationLoading(rawContent,
  cleanContent, isLoading) is the single source of truth. Show loading when
  (isLoading && hasCitationsBlock(rawContent)) or when
  (hasCitationsBlock(rawContent) && hasUnreplacedCitationRefs(cleanContent))
  so Pro/Ultra modes also show "loading citations" and half-finished
  [cite-N] never appear.

- message-group write_file: replace hasCitationsBlock + threadIsLoading
  with shouldShowCitationLoading(fileContent, cleanContent,
  threadIsLoading && isLast) for consistency.

- citations/utils: parse incomplete <citations> during streaming;
  remove isCitationsBlockIncomplete; keep hasUnreplacedCitationRefs
  internal; document display rule in file header.

Co-authored-by: Cursor <cursoragent@cursor.com>

---
feat(前端): 统一引用逻辑并杜绝半成品引用

- 新增 SafeCitationContent 作为引用正文的唯一出口：内部使用
  useParsedCitations + shouldShowCitationLoading，在引用未就绪时只显示
  「正在整理引用」，就绪后用 createCitationMarkdownComponents 渲染正文；
  支持可选 remarkPlugins、rehypePlugins、isHuman、img。

- 重构 MessageListItem：助手消息正文仅通过 SafeCitationContent 渲染，
  删除重复的 useParsedCitations、shouldShowCitationLoading、
  createCitationMarkdownComponents、CitationsLoadingIndicator 等逻辑；
  用户消息仍用 AIElementMessageResponse，不做引用解析。

- 澄清、present-files（message-list）、思考步骤与 write_file 加载
  （message-group）、子任务结果（subtask-card）均使用
  SafeCitationContent；Artifact 的 markdown 预览仍用同一 guard
  shouldShowCitationLoading，正文由 ArtifactFilePreview 渲染。

- 统一加载条件：shouldShowCitationLoading(rawContent, cleanContent,
  isLoading) 为唯一判断。在「流式中且已有引用块」或「有引用块且
  cleanContent 中仍有未替换的 [cite-N]」时仅显示加载，从而在 Pro/Ultra
  下也能看到「正在整理引用」，且永不出现半成品 [cite-N]。

- message-group 的 write_file：用 shouldShowCitationLoading(
  fileContent, cleanContent, threadIsLoading && isLast) 替代
  hasCitationsBlock + threadIsLoading，与其他场景一致。

- citations/utils：流式时解析未闭合的 <citations>；移除
  isCitationsBlockIncomplete；hasUnreplacedCitationRefs 保持内部使用；
  在文件头注释中说明展示规则。

frontend/src/components/workspace/artifacts/artifact-file-detail.tsx

@@ -21,7 +21,7 @@ import {
   ArtifactHeader,
   ArtifactTitle,
 } from "@/components/ai-elements/artifact";
-import { CitationAwareLink } from "@/components/ai-elements/inline-citation";
+import { createCitationMarkdownComponents } from "@/components/ai-elements/inline-citation";
 import { Select, SelectItem } from "@/components/ui/select";
 import {
   SelectContent,
@@ -32,11 +32,13 @@ import {
 import { ToggleGroup, ToggleGroupItem } from "@/components/ui/toggle-group";
 import { CodeEditor } from "@/components/workspace/code-editor";
 import { useArtifactContent } from "@/core/artifacts/hooks";
+import { CitationsLoadingIndicator } from "@/components/ai-elements/inline-citation";
 import { urlOfArtifact } from "@/core/artifacts/utils";
 import type { Citation } from "@/core/citations";
 import {
   contentWithoutCitationsFromParsed,
   removeAllCitations,
+  shouldShowCitationLoading,
   useParsedCitations,
 } from "@/core/citations";
 import { useI18n } from "@/core/i18n/hooks";
@@ -48,6 +50,8 @@ import { cn } from "@/lib/utils";
 
 import { Tooltip } from "../tooltip";
 
+import { useThread } from "../messages/context";
+
 import { useArtifacts } from "./context";
 
 export function ArtifactFileDetail({
@@ -89,6 +93,7 @@ export function ArtifactFileDetail({
   const previewable = useMemo(() => {
     return (language === "html" && !isWriteFile) || language === "markdown";
   }, [isWriteFile, language]);
+  const { thread } = useThread();
   const { content } = useArtifactContent({
     threadId,
     filepath: filepathFromProps,
@@ -248,14 +253,29 @@ export function ArtifactFileDetail({
       </ArtifactHeader>
       <ArtifactContent className="p-0">
         {previewable && viewMode === "preview" && (
-          <ArtifactFilePreview
-            filepath={filepath}
-            threadId={threadId}
-            content={content}
-            language={language ?? "text"}
-            cleanContent={parsed.cleanContent}
-            citationMap={parsed.citationMap}
-          />
+          language === "markdown" &&
+          content &&
+          shouldShowCitationLoading(
+            content,
+            parsed.cleanContent,
+            thread.isLoading,
+          ) ? (
+            <div className="flex size-full items-center justify-center p-4">
+              <CitationsLoadingIndicator
+                citations={parsed.citations}
+                className="my-0"
+              />
+            </div>
+          ) : (
+            <ArtifactFilePreview
+              filepath={filepath}
+              threadId={threadId}
+              content={content}
+              language={language ?? "text"}
+              cleanContent={parsed.cleanContent}
+              citationMap={parsed.citationMap}
+            />
+          )
         )}
         {isCodeFile && viewMode === "code" && (
           <CodeEditor
@@ -291,20 +311,16 @@ export function ArtifactFilePreview({
   citationMap: Map<string, Citation>;
 }) {
   if (language === "markdown") {
+    const components = createCitationMarkdownComponents({
+      citationMap,
+      syntheticExternal: true,
+    });
     return (
       <div className="size-full px-4">
         <Streamdown
           className="size-full"
           {...streamdownPlugins}
-          components={{
-            a: (props: React.AnchorHTMLAttributes<HTMLAnchorElement>) => (
-              <CitationAwareLink
-                {...props}
-                citationMap={citationMap}
-                syntheticExternal
-              />
-            ),
-          }}
+          components={components}
         >
           {cleanContent ?? ""}
         </Streamdown>