Hardcoded colors in 1.0.61 break the light themed CLI

### Describe the bug

Hardcoded background color breaks the light CMD theme.

### Affected version

GitHub Copilot CLI 1.0.61.

### Steps to reproduce the behavior

1. Set the light theme in Windows / Terminal
2. Run Github Copilot
3. Look at the screen

### Expected behavior

Allow reusing colors from Terminal Preview as many users set up the theme there.
Or, check if the Windows color scheme is light or dark before applying colors.
Many users are switching to light themes when working outdoors on a sunny day as the text is much better visible in such conditions.

### Additional context

_No response_

首先，使用 GitHub Copilot CLI 1.0.61 在採用淺色主題的 Windows Terminal 中重現問題，然後追蹤 CLI 色彩的初始化或套用位置。完成的標準是 CLI 不再強制使用深色背景，並遵循終端機或 Windows 的淺色/深色色彩設定；在淺色和深色主題下都驗證結果。

由索引模型根據 Issue 內容生成。