Scope PSModulePath modification to publish phase in release workflow

[Copilot]

Prepending artifacts/modules to PSModulePath in the local PSGallery validation step caused Import-Module IdLE to resolve the staged build output instead of the installed package from LocalRepo, allowing the validation gate to pass even when published packages had broken dependency wiring.

Changes

• Save original PSModulePath before modification
• Restore it after Publish-Module loop completes and before Install-Module/Import-Module verification
• Scopes the path mutation to only affect publishing operations, not install/import validation

  # Ensure required modules are discoverable during Test-ModuleManifest/Publish-Module.
+ # Save original PSModulePath to restore before install/import verification.
+ $originalPSModulePath = $env:PSModulePath
  $pathSeparator = [System.IO.Path]::PathSeparator
  ...
  
  foreach ($moduleName in $publishOrder) {
    Publish-Module -Path $modulePath -Repository 'LocalRepo' -ErrorAction Stop
  }

+ # Restore original PSModulePath before install/import verification
+ # to ensure Import-Module resolves the installed package, not the staged build.
+ $env:PSModulePath = $originalPSModulePath

  # Test that IdLE can be installed and imports correctly
  Install-Module -Name 'IdLE' -Repository 'LocalRepo' -Scope CurrentUser -Force

Addresses review feedback: #147 (comment)

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