refactor(frontend): simplify and deduplicate Citation-related code

- Extract removeCitationsBlocks in utils, reuse in parseCitations and removeAllCitations
- Add hasCitationsBlock; isCitationsBlockIncomplete now uses it
- Add useParsedCitations hook (parseCitations + buildCitationMap) for message/artifact
- Add CitationAwareLink to unify link rendering (message-list-item + artifact-file-detail)
- Add getCleanContent helper; message-group uses it and useParsedCitations
- ArtifactFileDetail: single useParsedCitations, pass cleanContent/citationMap to Preview
- Stop exporting buildCitationMap and removeCitationsBlocks from citations index
- Remove duplicate MessageLink and inline link logic in artifact preview

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

frontend/src/core/citations/index.ts

@@ -1,6 +1,7 @@
 export {
-  buildCitationMap,
   extractDomainFromUrl,
+  getCleanContent,
+  hasCitationsBlock,
   isCitationsBlockIncomplete,
   isExternalUrl,
   parseCitations,
@@ -8,4 +9,6 @@ export {
   syntheticCitationFromLink,
 } from "./utils";
 
+export { useParsedCitations } from "./use-parsed-citations";
+export type { UseParsedCitationsResult } from "./use-parsed-citations";
 export type { Citation, ParseCitationsResult } from "./utils";

frontend/src/core/citations/use-parsed-citations.ts

@@ -0,0 +1,28 @@
+"use client";
+
+import { useMemo } from "react";
+
+import { buildCitationMap, parseCitations } from "./utils";
+import type { Citation } from "./utils";
+
+export interface UseParsedCitationsResult {
+  citations: Citation[];
+  cleanContent: string;
+  citationMap: Map<string, Citation>;
+}
+
+/**
+ * Parse content for citations and build citation map. Memoized by content.
+ * Use in message and artifact components to avoid repeating parseCitations + buildCitationMap.
+ */
+export function useParsedCitations(content: string): UseParsedCitationsResult {
+  return useMemo(() => {
+    const parsed = parseCitations(content ?? "");
+    const citationMap = buildCitationMap(parsed.citations);
+    return {
+      citations: parsed.citations,
+      cleanContent: parsed.cleanContent,
+      citationMap,
+    };
+  }, [content]);
+}

frontend/src/core/citations/utils.ts

@@ -67,14 +67,7 @@ export function parseCitations(content: string): ParseCitationsResult {
     }
   }
 
-  // Remove ALL citations blocks from content (both complete and incomplete)
-  cleanContent = content.replace(/<citations>[\s\S]*?<\/citations>/g, "").trim();
-  
-  // Also remove incomplete citations blocks (during streaming)
-  // Match <citations> without closing tag or <citations> followed by anything until end of string
-  if (cleanContent.includes("<citations>")) {
-    cleanContent = cleanContent.replace(/<citations>[\s\S]*$/g, "").trim();
-  }
+  cleanContent = removeCitationsBlocks(content);
 
   // Convert [cite-N] references to markdown links
   // Example: [cite-1] -> [Title](url)
@@ -102,6 +95,13 @@ export function parseCitations(content: string): ParseCitationsResult {
   return { citations, cleanContent };
 }
 
+/**
+ * Return content with citations block removed and [cite-N] replaced by markdown links.
+ */
+export function getCleanContent(content: string): string {
+  return parseCitations(content ?? "").cleanContent;
+}
+
 /**
  * Build a map from URL to Citation for quick lookup
  *
@@ -153,6 +153,26 @@ export function extractDomainFromUrl(url: string): string {
   }
 }
 
+/**
+ * Remove all <citations> blocks from content (complete and incomplete).
+ * Does not remove [cite-N] or markdown links; use removeAllCitations for that.
+ */
+export function removeCitationsBlocks(content: string): string {
+  if (!content) return content;
+  let result = content.replace(/<citations>[\s\S]*?<\/citations>/g, "").trim();
+  if (result.includes("<citations>")) {
+    result = result.replace(/<citations>[\s\S]*$/g, "").trim();
+  }
+  return result;
+}
+
+/**
+ * Whether content contains a <citations> block (open tag).
+ */
+export function hasCitationsBlock(content: string): boolean {
+  return Boolean(content?.includes("<citations>"));
+}
+
 /**
  * Check if content is still receiving the citations block (streaming)
  * This helps determine if we should wait before parsing
@@ -161,15 +181,7 @@ export function extractDomainFromUrl(url: string): string {
  * @returns true if citations block appears to be incomplete
  */
 export function isCitationsBlockIncomplete(content: string): boolean {
-  if (!content) {
-    return false;
-  }
-
-  // Check if we have an opening tag but no closing tag
-  const hasOpenTag = content.includes("<citations>");
-  const hasCloseTag = content.includes("</citations>");
-
-  return hasOpenTag && !hasCloseTag;
+  return hasCitationsBlock(content) && !content.includes("</citations>");
 }
 
 /**
@@ -188,11 +200,8 @@ export function removeAllCitations(content: string): string {
     return content;
   }
 
-  let result = content;
-
   // Step 1: Remove all <citations> blocks (complete and incomplete)
-  result = result.replace(/<citations>[\s\S]*?<\/citations>/g, "");
-  result = result.replace(/<citations>[\s\S]*$/g, "");
+  let result = removeCitationsBlocks(content);
 
   // Step 2: Remove all [cite-N] references
   result = result.replace(/\[cite-\d+\]/g, "");