Issue Description

The Invoke-VerifiedDownload function in scripts/lib/Get-VerifiedDownload.ps1 has 0% test coverage. This 40-line function orchestrates file downloads with SHA256 verification but is completely untested.

Current state:

• File coverage: 29% line (22/76)
• Pure helper functions are well-tested (7 Describe blocks)
• Main orchestration function Invoke-VerifiedDownload has no tests

Acceptance criteria:

• Add Describe block for Invoke-VerifiedDownload in Get-VerifiedDownload.Tests.ps1
• Mock Invoke-WebRequest, Expand-Archive, and file system operations
• Test success path with valid hash
• Test failure path with hash mismatch
• Test skip path when valid file already exists
• Achieve ≥80% line coverage for the file

Estimated coverage improvement: 29% → ~82%

Additional Context

The existing test file pattern uses InModuleScope with mocked cmdlets. Follow the same approach used for Test-ExistingFileValid and Get-DownloadTargetPath tests.

This is part of a broader effort to increase unit test coverage from ~42% to ~85-90%.