Powershell tool requires `pwsh` and fails if I do not have it installed

[Tonychen0227]

Describe the bug

{"type":"tool.execution_complete","data":{"toolCallId":"toolu_vrtx_015T42XEjysw1jwbYmh9uEs2","success":false,"error":{"message":"<exited with error: PowerShell 6+ (pwsh) is not available. Please install it from https://aka.ms/powershell. Error: Error: Command failed: pwsh.exe --version\n'pwsh.exe' is not recognized as an internal or external command,\r\noperable program or batch file.\r\n>","code":"failure"},"toolTelemetry":{"properties":{"customTimeout":"true","executionMode":"sync"},"metrics":{"commandTimeout":180000}}},"id":"a5b01fca-e4e0-4d33-8ab7-6fde82c12015","timestamp":"2025-12-27T02:35:44.276Z","parentId":"6ef8d167-5161-4415-9eb7-76a21fe2f1a1"}

Repro steps:

Welcome to GitHub Copilot CLI
 Version 0.0.372 · Commit 5534560

 Copilot can write, test and debug code right from your terminal. Describe a task to get started or enter ? for help. Copilot uses AI, check for mistakes.

 ● Logged in as user: Tonychen0227

 ● Connected to GitHub MCP Server

 > Print hello world for me in powershell

Fails if pwsh is not available on the machine.

Affected version

0.0.372

Steps to reproduce the behavior

1. Type 'Print hello world for me in powershell' into Copilot on a machine without PWSH installed
2. Fails

Expected behavior

Should fallback to powershell instead of pwsh

Additional context

No response