Copilot doesn't support dark mode theme and some code color changes hard to see

**Describe the bug**

**Versions**
- Copilot for Xcode: 0.40.0
- Xcode: 26.0 beta 4 (17A5285i)
- macOS: 26.0 Beta(25A5316i)

**Steps to reproduce**
1. Open System Settings, Appearances, switch from light to dark and dark to light some times.
2. Copilot always shows in light mode and code color changes hard to see.

**Screenshots**

**Logs**

**Additional context**