Copilot Chat content not readable because jumpy

Does this issue occur when all extensions are disabled?: Yes

Version:
```
Version: 1.131.0
Commit: e4c7e7b1d6d060162f4aa7f8225271b67ce1df75
Date: 2026-07-28T10:51:25Z
Electron: 42.7.0
ElectronBuildId: 14710161
Chromium: 148.0.7778.280
Node.js: 24.18.0
V8: 14.8.178.38-electron.0
OS: Darwin arm64 25.6.0
```

### Steps to Reproduce

1. Ask GitHub Copilot Chat a question that results in multiple autonomous shell command executions (using **Allow All**).
2. Observe the shell command entries in the chat. Each command initially appears expanded, then collapses automatically, followed by the next command expanding and collapsing, and so on.

### Observed Behavior

The repeated expand/collapse animation causes the entire chat content above the current command to continuously jump up and down. This makes the conversation difficult to read because the text constantly shifts position, forcing the user to repeatedly relocate the point they were reading.

### Expected Behavior

When an expanded element collapses, the chat content above it should remain fixed in place. Instead of moving the content downward again, the UI should temporarily leave empty space where the expanded content was. Subsequent content can gradually fill that space as new output is added and the chat continues scrolling upward.

### Goal

The chat should never automatically move previously displayed content downward (unless the user explicitly scrolls with the mouse or keyboard). Automatic movement should only be upward, allowing the user's eyes to follow the content in a single direction.

Ideally, vertical movement should also be smooth (slightly animated) rather than jumpy, making the chat significantly easier to follow while new content is being generated.