Issue Description

Several scripts use inconsistent patterns for the "direct invocation vs dot-sourced" entry point guard. Some use $MyInvocation.InvocationName -ne '.' while the logic placement varies. Standardizing this pattern would improve consistency and testability across all scripts.

Additional Context

Current variations:

• Generate-PrReference.ps1: Uses if ($MyInvocation.InvocationName -ne '.') { ... } at the end
• Get-VerifiedDownload.ps1: Same pattern but with different error handling
• Package-Extension.ps1: Same pattern with extensive inline logic

Recommended approach:

1. Ensure all scripts use the same guard pattern at the end of the file
2. Extract main logic into a named function (e.g., Invoke-*) that the guard calls
3. Document the pattern in scripts/README.md for future contributors

Testing:

• Dot-source each script and verify functions are available
• Run each script directly and verify expected behavior
• Run existing Pester tests that rely on dot-sourcing