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-CN.json

@@ -1439,7 +1439,9 @@
         "cancel": "取消",
         "send": "发送",
         "forkAndSend": "分叉发送",
-        "slashCommands": "斜杠命令"
+        "slashCommands": "斜杠命令",
+        "expertSkills": "专家技能",
+        "expertsEmptyForAgent": "该智能体没有启用任何专家。请在「设置 > 专家」中启用。"
       },
       "messageQueue": {
         "addToQueue": "加入队列",