Copilot CLI internal PowerShell tool fails to spawn pwsh.exe on Windows (ENOENT)

### Describe the bug

The Copilot CLI works correctly for interactive prompts, but its internal PowerShell tool runtime fails to execute pwsh.exe on this Windows machine.
PowerShell 7 is installed, accessible, and resolves correctly via PATH. The failure is limited to Copilot CLI’s internal command execution (Node.js spawn).
This appears to be a Copilot CLI tool runtime issue rather than an environment misconfiguration.

### Affected version

Copilot CLI: v1.0.12 installed via winget

### Steps to reproduce the behavior

Steps to Reproduce

Install PowerShell 7.6.0 via winget
Ensure pwsh.exe is accessible via PATH
Install Copilot CLI via winget
Run a Copilot CLI workflow that requires internal PowerShell execution

### Expected behavior

Copilot CLI should be able to spawn pwsh.exe and execute PowerShell commands successfully.

### Additional context

The following commands work correctly when executed directly in PowerShell:
where pwsh
(Get-Command pwsh).Source

Both resolve to:
C:\Program Files\PowerShell\7\pwsh.exe
pwsh -NoLogo -Command "$PSVersionTable.PSVersion"

Environment

OS: Windows (64-bit)
Copilot CLI: v1.0.12 installed via winget
Installation type: WinGet / MSIX
PowerShell: 7.6.0 (x64)

Installation path: C:\Program Files\PowerShell\7\pwsh.exe
PowerShell x86 was removed to avoid multi-architecture conflicts
The issue persists even with a clean PATH and fresh sessions
This suggests a Copilot CLI internal tool runtime / MSIX sandbox limitation
Junctions and PATH fixes do not resolve the issue