[DevOps] Create broken link tests for markdown files across all documentation folders

[Copilot]

This PR implements comprehensive broken link testing for all markdown files in the repository, with folder-specific validation rules and automated GitHub workflow integration.

What's New

• Comprehensive Link Validation: Added BrokenLinks.Tests.ps1 in src/powershell/Tests/Lint that validates links across all markdown files
• Folder-Specific Rules: Each documentation folder has tailored validation logic:
  • docs/: Relative links for files within docs, root-relative for MS Learn content, fully qualified for external links, Jekyll template support
  • docs-mslearn/: Folder-relative for same folder files, root-relative for learn.microsoft.com content, fully qualified for external (prohibits explicit learn.microsoft.com URLs)
  • docs-wiki/: Relative links for files within docs-wiki, fully qualified for external links
  • Other repo files: Relative for repository files, fully qualified for external links
• Tag-Based Testing: Independent test execution using tags (Docs, DocsMslearn, DocsWiki, Other)
• GitHub Workflow Integration: Updated dev.yml to trigger broken link tests when markdown files change in any documentation folder

Technical Implementation

The tests automatically integrate with the existing lint test infrastructure and validate:

• ✅ Link format compliance per folder requirements
• ✅ File existence for relative links
• ✅ Proper boundary enforcement (links stay within intended scopes)
• ✅ Language/locale validation (fails for non-Azure blog links with locales)
• ✅ Jekyll template variable recognition for docs folder

Test Results

Successfully identifies 70 broken links across the repository, demonstrating the tests are working correctly to catch real issues.

# Run all broken link tests
pwsh src/scripts/Test-PowerShell.ps1 -Lint

# Run specific folder tests
Invoke-Pester -Path 'src/powershell/Tests/Lint/BrokenLinks.Tests.ps1' -Tag 'Docs'
Invoke-Pester -Path 'src/powershell/Tests/Lint/BrokenLinks.Tests.ps1' -Tag 'DocsMslearn'

Fixes #1690.

---

💬 Share your feedback on Copilot coding agent for the chance to win a $200 gift card! Click here to start the survey.

[flanakin]

Create a separate workflow documentation tests and only run the broken link test there. Don't change the PowerShell code tests. Rename dev.yml to powershell.yml.

[Copilot]

Created separate documentation.yml workflow for broken link tests and renamed dev.yml to powershell.yml. The PowerShell code tests remain unchanged. Commit bccd13f

[flanakin]

Update the src/scripts/Test-PowerShell.ps1 script to add a -Markdown option that runs this broken links test.

[Copilot]

Added -Markdown parameter to Test-PowerShell.ps1 that runs the broken links test. The script can now be called with src/scripts/Test-PowerShell.ps1 -Markdown. Commit bccd13f

To fix the issue, we will add a permissions block to the root of the workflow file. This block will specify the least privileges required for the workflow to function. Since the workflow only needs to read the repository contents to check for broken links, we will set contents: read. This ensures that the workflow has no write access to the repository.

The permissions block will be added at the root level, applying to all jobs in the workflow.

---