Copilot CLI 1.0.64 and 1.0.65 on VSCode terminal ignores user theme and defaults to light theme.

### Describe the bug

Since the Copilot CLI 1.0.64 release, the VSCode terminal no longer respects the user's theme and defaults to a light theme instead.

I have tested this with both Dark and Solarized themes; however, the Copilot CLI terminal always displays the light theme regardless of the active setting.

### Affected version

Github Copilot CLI 1.0.64, Github Copilot CLI 1.0.65

### Steps to reproduce the behavior

1. Run copilot within a VSCode terminal.
2. If you are using a VSCode theme different than light, the copilot cli will change terminal theme to light, ignoring user's theme.

### Expected behavior

Copilot CLI respects user's theme as of version 1.0.63.

### Additional context

- Operating System: Windows 11 25H2
- Shell: bash
- Terminal emulator: VSCode 1.126.0 - devcontainer alpine linux 3.22.2
- CPU Arch: X86_64
- Binary: [github-copilot-1.0.65-linuxmusl-x64.tgz](https://github.com/github/copilot-cli/releases/download/v1.0.65/github-copilot-1.0.65-linuxmusl-x64.tgz)

在带有 Dark 或 Solarized 主题的 VSCode 终端中运行 Copilot CLI 1.0.64 或 1.0.65 来复现该问题，并尽可能使用所报告的 Windows 11、bash 和 devcontainer 上下文。将其行为与版本 1.0.63 进行比较，并跟踪终端主题的处理；当 CLI 保留当前活动的 VSCode 主题而不是切换为浅色主题时，即表示完成。

由索引模型根据 Issue 内容生成。