Use ; instead of && for chaining commands on PowerShell (Windows)

[8u9i]

Description: Command Code generates shell commands using && to chain multiple operations. While this works in Unix shells (bash/zsh), Windows
PowerShell requires ; as the command separator. On Windows systems running PowerShell, commands with && fail with syntax errors.

Steps to reproduce:

1. Use Command Code on Windows with PowerShell as the shell
2. Request any task that generates chained commands (e.g., "install dependencies and run build")
3. Observe that generated commands use && instead of ;

Expected behavior: Command Code should detect the shell environment and use ; when on PowerShell/Windows.

Environment:

• OS: Windows 10.0.26200
• Terminal: WezTerm
• Shell: cmd.exe / PowerShell