[Bug]: Long loading time for long chats

### Platform

Linux

### Operating system version

Ubuntu 24.04

### System architecture

Intel (x86)

### PolyScope Version

0.17 (latest for Linux sadly)

### Bug description

When the chats are long, the loading time is long and polyscope is unable to detect whether a chat is still running with claude or not. This makes it unclear whether it is working on something or not.

### Steps to reproduce

1. Create long running chats with a lot of prompts. You can compact etc.
2. Switching between chats takes a longer time.
3. Polyscope does not know anymore whether a chat is still running in the agent.

### Relevant log output

```shell

```

首先，在 Linux/Ubuntu 24.04 上使用持续时间较长的聊天和大量 prompt 重现该问题，然后检查聊天切换的加载路径以及 agent 运行状态的处理方式。当在较长的聊天之间切换不再产生过长的加载时间，并且 Polyscope 能够可靠地指示 agent 是否仍在运行时，即视为完成。

由索引模型根据 Issue 内容生成。