I/O Exception when navigating Plugins settings quickly

### Short summary

I/O exception toast when expanding plugin collections and failed refresh

### Affected version or release

v1.1.2

### Installation context

Windows

### What happened?

When expanding the plugins catalog and installed plugins quickly, a race condition seems to be causing I/O exceptions shown in the toast notifications.
Unfortunately, I did not manage to grab the exception in the screenshot before it disappeared. However, I found the exception in the app log file.

### Steps to reproduce

This issue seems like a rare edge case where the following conditions must be met in order to reproduce the issue:
1. A plugin catalog must exist in the plugins settings
2. A plugin must be installed already from the same plugin catalog already
3. The list of plugins in a catalog must not be fetched are cached already
- In my case, I reopened the app after not using it for 3 weeks. I don't know how to recreate this setting.

**Steps to reproduce:**
1. Go to settings
2. Go to the plugins settings
3. In the "All tab", expand a plugin collection which forces a refresh of the catalog
4. Then, quickly change tab to "Installed" and expand one of the installed plugins
5. Wait for a while
6. Try again without switching tabs and expanding groups fast
7. Now it works and won't happen again

### Expected behavior

Plugins catalog list refreshes without an exception.

### Additional context

**App logs:**
```
2026-07-30T06:53:54.820218Z DEBUG task_spawn{task="ws_handle_connection"}:task_spawn{task="ws_recv_loop"}: github_app::websocket: received message kind="browse_plugin_marketplace" text={"type":"browse_plugin_marketplace","name":"awesome-copilot"}
2026-07-30T06:53:56.525169Z ERROR task_spawn{task="ws_handle_connection"}:task_spawn{task="ws_recv_loop"}:task_spawn{task="ws_handle_client_message" kind="browse_plugin_marketplace"}: github_app::handlers::plugins_config: failed to browse plugin marketplace error=RPC error -32603: Request plugins.marketplaces.browse failed with message: Failed to fetch GitHub marketplace github/awesome-copilot: Git cache I/O failed: The process cannot access the file because it is being used by another process. (os error 32) name=awesome-copilot
2026-07-30T06:53:59.291863Z DEBUG github_app::metrics::client: metrics batch sent to CAFE count=15
2026-07-30T06:53:59.677390Z DEBUG task_spawn{task="ws_handle_connection"}:task_spawn{task="ws_recv_loop"}: github_app::websocket: received message kind="browse_plugin_marketplace" text={"type":"browse_plugin_marketplace","name":"awesome-copilot"}
2026-07-30T06:54:01.328795Z ERROR task_spawn{task="ws_handle_connection"}:task_spawn{task="ws_recv_loop"}:task_spawn{task="ws_handle_client_message" kind="browse_plugin_marketplace"}: github_app::handlers::plugins_config: failed to browse plugin marketplace error=RPC error -32603: Request plugins.marketplaces.browse failed with message: Failed to fetch GitHub marketplace github/awesome-copilot: Git cache I/O failed: The process cannot access the file because it is being used by another process. (os error 32) name=awesome-copilot

```