Merge upstream/experimental into feat/citations

Resolved conflicts:
- backend/src/gateway/routers/artifacts.py: Keep citations block removal for markdown downloads
- frontend/src/components/workspace/messages/message-list-item.tsx: Keep improved citation handling with rehypePlugins, humanMessagePlugins, and CitationsLoadingIndicator

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

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

@@ -77,7 +77,11 @@ 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: "专业",
     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: "超级",
+    ultraModeDescription: "专业模式加子代理，适用于复杂的多步骤任务，功能最强大",
     searchModels: "搜索模型...",
+    surpriseMe: "小惊喜",
+    surpriseMePrompt: "给我一个小惊喜吧",
     suggestions: [
       {
         suggestion: "写作",
@@ -209,7 +213,7 @@ export const zhCN: Translations = {
       tools: "工具",
       skills: "技能",
       notification: "通知",
-      acknowledge: "致谢",
+      about: "关于",
     },
     memory: {
       title: "记忆",