[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.

Written by the indexing model from the issue text.