When files encoded in Windows 1252 are edited, Copilot changes the encoding to UTF-8.

### Describe the bug

Copilot doesn't respect the original file encoding; it makes edits and changes the file format to UTF-8. I haven't found a prompt to prevent this from happening.

What it does, after saving the wrong file, is try to revert the encoding using scripts.

### Affected version

GitHub Copilot CLI 1.0.56.

### Steps to reproduce the behavior

1) Create a Windows1252 file and save in repo;
2) Ask the copilot to make changes.

### Expected behavior

Copilot needs to respect file encoding

### Additional context

_No response_

使用 Windows 1252 文件在 GitHub Copilot CLI 1.0.56 中重现该问题，然后跟踪 Copilot 修改该文件时使用的编辑和保存路径。确认编辑会保留原始编码，并根据报告的重现步骤验证行为；issue 中没有指定源文件或测试。

由索引模型根据 Issue 内容生成。