macOS: Send/Stop button stuck in processing after AI reply, manual Stop causes paused chat and occasional freeze

On macOS, sometimes after the AI finishes replying, the Send/Stop button in the bottom-right corner remains in a processing state. If I manually click Stop, I can no longer send messages in the dialog box with a "paused" prompt displayed, and occasionally the program freezes.

查找处理 Send/Stop 按钮状态的 UI 组件，该组件可能位于 macOS 专用的 frontend 模块中。检查管理聊天交互和 AI 响应的事件循环或状态机。触发 AI 回复并观察按钮的状态转换，以重现该问题。检查 AI 完成后是否存在竞态条件或未处理的状态。

由索引模型根据 Issue 内容生成。