Broken light theme

### Describe the bug

I suspect the black background on the user prompt is the result of a broken config. The text is very difficult to read due to the low colour contrast. The same issue affects the selection highlight, which also lacks sufficient visibility.

### Affected version

GitHub Copilot CLI 1.0.61.

### Steps to reproduce the behavior

Switch to light theme.

### Expected behavior

Have a lighter colour for highlight and for prompts, if any. I don't see why prompts need any background colour.

### Additional context

_No response_