a981be62f4
7-Zip MSI installer adds to system PATH but PowerShell session doesn't
see it until PATH is refreshed. Refresh via:
$env:PATH = [System.Environment]::GetEnvironmentVariable('PATH', 'Machine') + ';' +
[System.Environment]::GetEnvironmentVariable('PATH', 'User')
Same pattern already used for Git installer. Fixes validation error:
'7z command resolvable' now passes after installation.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>