Windows 上允许配置 Shell 执行器（支持使用 bash/zsh 替代 PowerShell） || Allow configuration of Shell executor on Windows (supports using bash/zsh instead of PowerShell)

[zhatlas]

What version of Kimi Code CLI is running?

1.27.0

Which open platform/subscription were you using?

Allegretto

Which model were you using?

kimi-for-coding

What platform is your computer?

Microsoft Windows NT 10.0.19045.0 x64

What issue are you seeing?

目前，在 Windows 上，Shell 工具固定使用 PowerShell (powershell.exe) 作为底层 shell 执行器。这是硬编码的行为，用户无法更改。

问题在于 PowerShell 与 bash/zsh 语法不同：

• && 和 || 运算符在 PowerShell 中无效（旧版本）
• 许多常用的 Unix/Linux 命令和工具无法直接使用
• 安装了 Git Bash 的用户无法利用它来获得更好的命令兼容性

例如，尝试运行：

where git bash 2>nul || where bash 2>nul
会导致错误：The token '||' is not a valid statement separator in this version.
虽然用户可以通过手动使用完整路径调用 bash 来解决这个问题，但如果能配置 shell 执行器会更加方便。

### What steps can reproduce the bug?

1. 在 Windows 上安装 Git Bash，路径为 `D:\Program Files\Git\usr\bin\bash.exe`
2. 让 Kimi Code CLI 使用 bash 语法执行命令（例如使用 `&&` 或 `||`）
3. 观察到 PowerShell 因语法差异而拒绝执行这些命令

### What is the expected behavior?

1. 允许用户通过以下方式配置首选的 shell 执行器：
   - 环境变量（例如 `KIMI_CLI_SHELL`）
   - 配置文件设置
   - 或自动检测 Git Bash/WSL 是否可用

2. 配置示例：
   ```json
   {
     "shell": {
       "windows": "D:\\Program Files\\Git\\usr\\bin\\bash.exe"
     }
   }
3. 当配置为 bash 时，Shell 工具应该使用 bash 而不是 PowerShell 来执行命令，从而更好地兼容 Unix 风格的命令和工具。
这将显著改善在混合 Unix/Windows 环境中工作的 Windows 用户的体验。

### Additional information

_No response_
<!--This is a translation content dividing line, the content below is generated by machine, please do not modify the content below-->
---
### What version of Kimi Code CLI is running?

1.27.0

### Which open platform/subscription were you using?

Allegretto

### Which model were you using?

kimi-for-coding

### What platform is your computer?

Microsoft Windows NT 10.0.19045.0 x64

### What issue are you seeing?

Currently, on Windows, the `Shell` tool consistently uses PowerShell (`powershell.exe`) as the underlying shell executor. This is hard-coded behavior and cannot be changed by the user.

The problem is that PowerShell has different syntax than bash/zsh:
- `&&` and `||` operators do not work in PowerShell (old version)
- Many commonly used Unix/Linux commands and tools cannot be used directly
- Users with Git Bash installed cannot take advantage of it for better command compatibility

For example, try running:
```powershell
where git bash 2>nul || where bash 2>nul
will result in the error: The token '||' is not a valid statement separator in this version.
Although the user can solve this problem by manually calling bash with the full path, it would be more convenient if the shell executor can be configured.

### What steps can reproduce the bug?

1. Install Git Bash on Windows, the path is `D:\Program Files\Git\usr\bin\bash.exe`
2. Let Kimi Code CLI execute the command using bash syntax (e.g. using `&&` or `||`)
3. Observe that PowerShell refuses to execute these commands due to syntax differences

### What is the expected behavior?

1. Allow users to configure their preferred shell executor via:
   - Environment variables (e.g. `KIMI_CLI_SHELL`)
   - Profile settings
   - Or automatically detect whether Git Bash/WSL is available

2. Configuration example:
   ```json
   {
     "shell": {
       "windows": "D:\\Program Files\\Git\\usr\\bin\\bash.exe"
     }
   }
3. When configured as bash, the Shell tool should use bash instead of PowerShell to execute commands for better compatibility with Unix-style commands and tools.
This will significantly improve the experience for Windows users working in mixed Unix/Windows environments.

### Additional information

_No response_