refactor(frontend): consolidate citation logic, slim exports and impl

- SafeCitationContent: add loadingOnly and renderBody props.
  - loadingOnly: show only loading indicator or null (e.g. write_file step).
  - renderBody(parsed): custom body renderer (e.g. artifact preview).

- message-group write_file: use SafeCitationContent(content, isLoading,
  rehypePlugins, loadingOnly) instead of local useParsedCitations +
  shouldShowCitationLoading + CitationsLoadingIndicator. Pass rehypePlugins
  into ToolCall.

- artifact-file-detail markdown preview: use SafeCitationContent with
  renderBody((p) => <ArtifactFilePreview ... cleanContent={p.cleanContent}
  citationMap={p.citationMap} />). Remove local shouldShowCitationLoading
  and CitationsLoadingIndicator branch.

- core/citations: inline buildCitationMap into use-parsed-citations, remove
  from utils; stop exporting hasCitationsBlock (internal to shouldShowCitationLoading).

- inline-citation: make InlineCitationCard, InlineCitationCardBody,
  InlineCitationSource file-private (no longer exported).

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

---
refactor(前端): 收拢引用逻辑、精简导出与实现

- SafeCitationContent 新增 loadingOnly、renderBody。
  - loadingOnly：仅显示加载或 null（如 write_file 步骤）。
  - renderBody(parsed)：自定义正文渲染（如 artifact 预览）。

- message-group write_file：改用 SafeCitationContent(loadingOnly)，去掉
  本地 useParsedCitations + shouldShowCitationLoading + CitationsLoadingIndicator，
  并向 ToolCall 传入 rehypePlugins。

- artifact-file-detail 的 markdown 预览：改用 SafeCitationContent +
  renderBody 渲染 ArtifactFilePreview，去掉本地加载判断与
  CitationsLoadingIndicator 分支。

- core/citations：buildCitationMap 内联到 use-parsed-citations 并从 utils
  删除；hasCitationsBlock 不再导出（仅 shouldShowCitationLoading 内部使用）。

- inline-citation：InlineCitationCard/Body/Source 改为文件内私有，不再导出。

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

@@ -22,10 +22,8 @@ import {
   ChainOfThoughtStep,
 } from "@/components/ai-elements/chain-of-thought";
 import { CodeBlock } from "@/components/ai-elements/code-block";
-import { CitationsLoadingIndicator } from "@/components/ai-elements/inline-citation";
 import { MessageResponse } from "@/components/ai-elements/message";
 import { Button } from "@/components/ui/button";
-import { shouldShowCitationLoading, useParsedCitations } from "@/core/citations";
 import { useI18n } from "@/core/i18n/hooks";
 import {
   extractReasoningContentFromMessage,
@@ -130,7 +128,12 @@ export function MessageGroup({
                   }
                 ></ChainOfThoughtStep>
               ) : (
-                <ToolCall key={step.id} {...step} isLoading={isLoading} />
+                <ToolCall
+                  key={step.id}
+                  {...step}
+                  isLoading={isLoading}
+                  rehypePlugins={rehypePlugins}
+                />
               ),
             )}
           {lastToolCallStep && (
@@ -140,6 +143,7 @@ export function MessageGroup({
                 {...lastToolCallStep}
                 isLast={true}
                 isLoading={isLoading}
+                rehypePlugins={rehypePlugins}
               />
             </FlipDisplay>
           )}
@@ -197,6 +201,7 @@ function ToolCall({
   result,
   isLast = false,
   isLoading = false,
+  rehypePlugins,
 }: {
   id?: string;
   messageId?: string;
@@ -205,6 +210,7 @@ function ToolCall({
   result?: string | Record<string, unknown>;
   isLast?: boolean;
   isLoading?: boolean;
+  rehypePlugins: ReturnType<typeof useRehypeSplitWordsIntoSpans>;
 }) {
   const { t } = useI18n();
   const { setOpen, autoOpen, autoSelect, selectedArtifact, select } =
@@ -213,7 +219,6 @@ function ToolCall({
   const threadIsLoading = thread.isLoading;
 
   const fileContent = typeof args.content === "string" ? args.content : "";
-  const { citations, cleanContent } = useParsedCitations(fileContent);
 
   if (name === "web_search") {
     let label: React.ReactNode = t.toolCalls.searchForRelatedInfo;
@@ -362,13 +367,6 @@ function ToolCall({
     const isMarkdown =
       path?.toLowerCase().endsWith(".md") ||
       path?.toLowerCase().endsWith(".markdown");
-    const showCitationsLoading =
-      isMarkdown &&
-      shouldShowCitationLoading(
-        fileContent,
-        cleanContent,
-        threadIsLoading && isLast,
-      );
 
     return (
       <>
@@ -392,10 +390,14 @@ function ToolCall({
             </ChainOfThoughtSearchResult>
           )}
         </ChainOfThoughtStep>
-        {showCitationsLoading && (
-          <div className="mt-2 ml-8">
-            <CitationsLoadingIndicator citations={citations} />
-          </div>
+        {isMarkdown && (
+          <SafeCitationContent
+            content={fileContent}
+            isLoading={threadIsLoading && isLast}
+            rehypePlugins={rehypePlugins}
+            loadingOnly
+            className="mt-2 ml-8"
+          />
         )}
       </>
     );