[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

```

Start by reproducing the issue on Linux/Ubuntu 24.04 with long-running chats and many prompts, then inspect the chat-switching load path and agent-running status handling. Done means switching between long chats no longer incurs excessive loading time and Polyscope reliably indicates whether the agent is still running.

Rédigé par le modèle d'indexation à partir du texte de l'issue.