Scroll bar jumps erratically during model response generation

[IkerJansa44]

Describe the bug

When using the Copilot CLI, the scroll bar sometimes behaves unpredictably while a model is generating a response. This issue occurs intermittently but is disruptive to usability.

Affected version

v0.0.330 Commit: a8bfefe

Steps to reproduce the behavior

1. Run the Copilot CLI and generate a response.
2. Let the model continue generating for a while (longer outputs seem to trigger it).
3. Observe the scroll bar jumping up and down unexpectedly.

It's happened multiple times, but this is the ID of a particular session that had this behaviour
Session ID: 00e74102-bd77-4cdc-8981-d8d8df1433e0

Expected behavior

The scroll bar should remain stable and smoothly follow the output as it is generated.

Additional context

No response

[nathfavour]

I think this is somewhat related to the flicker issue opened approx. 2 hours ago: #158