"Waiting" state does not explain current agent activity

## Reported behavior

A user reported that sessions can show "Waiting" for several minutes without any indication of what the agent is doing.

This makes it difficult to tell whether the agent is thinking, compacting context, waiting on a service, or stuck.

## Expected behavior

When a session shows "Waiting," users should be able to see the current activity or status. The app does not need to expose chain of thought, but it should provide enough information to show that work is continuing and where time is being spent.

没有指定文件或测试。首先定位呈现“Waiting”状态的桌面 UI，并追踪 agent 活动是如何表示的；当用户能够在不暴露 chain of thought 的情况下区分正在进行的工作（例如思考、上下文压缩、等待服务或卡住的会话）时，即表示完成。

由索引模型根据 Issue 内容生成。