Merge upstream/experimental and resolve conflicts; citations + path_utils + mode-hover

## 冲突解决 (Resolve conflicts)
- input-box.tsx: 保留 ModeHoverGuide 包裹的模式选择器（PR #26 的 mode-hover-guide）
- message-group.tsx: 保留 getCleanContent / hasCitationsBlock / useParsedCitations
- message-list-item.tsx: 保留 useParsedCitations，移除重复的 MessageLink（使用 CitationAwareLink）
- artifact-file-detail.tsx: 保留 CitationAwareLink、useParsedCitations、contentWithoutCitationsFromParsed
- artifacts.py: 保留 path_utils 与 _extract_citation_urls + remove_citations_block 精简实现
- citations/index.ts: 保留并补充 contentWithoutCitationsFromParsed 导出
- en-US.ts: 保留 Ultra 模式描述 "Reasoning, planning and execution with subagents..."
- zh-CN.ts: 保留「超级」标签，描述保留「思考、计划并执行，可调用子代理分工协作...」

## PR #26 代码改动汇总

### 1. Citations（引用）
- lead_agent prompt: 增加 Web search 与子代理合成时的 citation 提示
- general_purpose: 子代理 system prompt 增加 <citations_format> 说明
- frontend utils: 新增 contentWithoutCitationsFromParsed，removeAllCitations 基于单次解析
- frontend artifact: 使用 contentWithoutCitationsFromParsed(parsed) 避免对同一内容解析两次
- backend artifacts: _extract_citation_urls + remove_citations_block，json 提到顶部

### 2. path_utils（路径解析）
- 新增 backend/src/gateway/path_utils.py：resolve_thread_virtual_path，防 path traversal
- artifacts.py / skills.py：删除内联路径解析，统一使用 path_utils

### 3. Mode hover guide
- input-box: 模式选择器外包 ModeHoverGuide，悬停展示模式说明

### 4. i18n
- en: ultraModeDescription 与 zh: ultraMode / ultraModeDescription 与上游对齐并保留 PR 文案

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

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

@@ -34,7 +34,11 @@ import { CodeEditor } from "@/components/workspace/code-editor";
 import { useArtifactContent } from "@/core/artifacts/hooks";
 import { urlOfArtifact } from "@/core/artifacts/utils";
 import type { Citation } from "@/core/citations";
-import { removeAllCitations, useParsedCitations } from "@/core/citations";
+import {
+  contentWithoutCitationsFromParsed,
+  removeAllCitations,
+  useParsedCitations,
+} from "@/core/citations";
 import { useI18n } from "@/core/i18n/hooks";
 import { installSkill } from "@/core/skills/api";
 import { streamdownPlugins } from "@/core/streamdown";
@@ -96,12 +100,10 @@ export function ArtifactFileDetail({
   );
   const cleanContent =
     language === "markdown" && content ? parsed.cleanContent : (content ?? "");
-  const contentWithoutCitations = useMemo(() => {
-    if (language === "markdown" && content) {
-      return removeAllCitations(content);
-    }
-    return content;
-  }, [content, language]);
+  const contentWithoutCitations =
+    language === "markdown" && content
+      ? contentWithoutCitationsFromParsed(parsed)
+      : (content ?? "");
 
   const [viewMode, setViewMode] = useState<"code" | "preview">("code");
   const [isInstalling, setIsInstalling] = useState(false);

frontend/src/core/citations/index.ts

@@ -1,4 +1,5 @@
 export {
+  contentWithoutCitationsFromParsed,
   extractDomainFromUrl,
   getCleanContent,
   hasCitationsBlock,

frontend/src/core/citations/utils.ts

@@ -185,27 +185,25 @@ export function isCitationsBlockIncomplete(content: string): boolean {
 }
 
 /**
- * Remove ALL citations from content, including:
- * - <citations> blocks
- * - [cite-N] references (and their converted markdown links)
- *
- * Uses parseCitations once, then strips citation links from cleanContent.
- * Used for copy/download to produce content without any citation references.
- *
- * @param content - The raw content that may contain citations
- * @returns Content with all citations completely removed
+ * Strip citation markdown links from already-cleaned content (from parseCitations).
+ * Use when you already have ParseCitationsResult to avoid parsing twice.
  */
-export function removeAllCitations(content: string): string {
-  if (!content) return content;
-
-  const parsed = parseCitations(content);
+export function contentWithoutCitationsFromParsed(
+  parsed: ParseCitationsResult,
+): string {
   const citationUrls = new Set(parsed.citations.map((c) => c.url));
-
-  // Remove markdown links that point to citation URLs; keep non-citation links
   const withoutLinks = parsed.cleanContent.replace(
     /\[([^\]]+)\]\(([^)]+)\)/g,
     (fullMatch, _text, url) => (citationUrls.has(url) ? "" : fullMatch),
   );
-
   return withoutLinks.replace(/\n{3,}/g, "\n\n").trim();
 }
+
+/**
+ * Remove ALL citations from content (blocks, [cite-N], and citation links).
+ * Used for copy/download. For display you typically use parseCitations/useParsedCitations.
+ */
+export function removeAllCitations(content: string): string {
+  if (!content) return content;
+  return contentWithoutCitationsFromParsed(parseCitations(content));
+}

frontend/src/core/i18n/locales/zh-CN.ts

@@ -77,7 +77,7 @@ export const zhCN: Translations = {
     reasoningModeDescription: "思考后再行动，在时间与准确性之间取得平衡",
     proMode: "Pro",
     proModeDescription: "思考、计划再执行，获得更精准的结果，可能需要更多时间",
-    ultraMode: "Ultra",
+    ultraMode: "超级",
     ultraModeDescription:
       "思考、计划并执行，可调用子代理分工协作，适合复杂多步骤任务，能力最强",
     searchModels: "搜索模型...",