feat(chat): add experts menu to message input toolbar

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/i18n/messages/zh-TW.json

@@ -1439,7 +1439,9 @@
         "cancel": "取消",
         "send": "傳送",
         "forkAndSend": "分叉發送",
-        "slashCommands": "斜線命令"
+        "slashCommands": "斜線命令",
+        "expertSkills": "專家技能",
+        "expertsEmptyForAgent": "該智慧代理沒有啟用任何專家。請在「設定 > 專家」中啟用。"
       },
       "messageQueue": {
         "addToQueue": "加入佇列",