[Requests and ideas] Display sub-agent model

**Mood:** 😊
**Category:** Requests and ideas

My main agents often delegate tasks to sub-agents. For debugging purpose and to improve my harness, I would like to know which model is actually used by sub-agents.

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| Field | Value |
| --- | --- |
| App version | 1.0.6 |
| OS | Windows 10.0.26200 |
| Theme | Fox |
| Path | /chat |
| Tenure | Week 5 |

未指定文件或测试；从 /chat 体验开始，调查 sub-agent 的活动显示在哪里。当每个 sub-agent 实际使用的模型都能显示出来以便调试时，即视为完成。

由索引模型根据 Issue 内容生成。