fix(extension): inline agent content instead of path stubs in packaged plugins

[stablegenius49]

Pull Request

Description

When plugins are packaged in non-symlink environments (e.g., Windows without Developer Mode, or when Copilot CLI installs plugins), agent files were being written as single-line relative path references instead of actual YAML frontmatter content. This caused Copilot CLI to fail with 'frontmatter is malformed' errors on all agent files.

Root Cause

The New-PluginLink function was writing text stubs containing relative paths when symlinks were not supported. The Copilot CLI expects agent .md files to begin with valid YAML frontmatter (--- delimited block with at least a description field), but received single-line path strings instead.

Fix

Changed New-PluginLink to copy the actual file content when symlinks are not supported, ensuring agent files have valid YAML frontmatter in installed plugins.

Before:

else {
    [System.IO.File]::WriteAllText($DestinationPath, $relativePath)
}

After:

else {
    # Copy the actual file content instead of writing a path reference
    # This ensures agent files have valid YAML frontmatter in installed plugins
    Copy-Item -Path $SourcePath -Destination $DestinationPath -Force
}

Related Issue(s)

Fixes #785

Type of Change

Select all that apply:

Code & Documentation:

• Bug fix (non-breaking change fixing an issue)
• New feature (non-breaking change adding functionality)
• Breaking change (fix or feature causing existing functionality to change)
• Documentation update

Infrastructure & Configuration:

• GitHub Actions workflow
• Linting configuration (markdown, PowerShell, etc.)
• Security configuration
• DevContainer configuration
• Dependency update

AI Artifacts:

• Reviewed contribution with prompt-builder agent and addressed all feedback
• Copilot instructions (.github/instructions/*.instructions.md)
• Copilot prompt (.github/prompts/*.prompt.md)
• Copilot agent (.github/agents/*.agent.md)
• Copilot skill (.github/skills/*/SKILL.md)

Other:

• Script/automation (.ps1, .sh, .py)
• Other (please describe):

Testing

This fix ensures:

• Agent files have valid YAML frontmatter when installed via copilot plugin install
• Commands, instructions, and skills continue to work correctly
• Plugin packaging works in both symlink and non-symlink environments

Validation

• Local testing shows agent files now contain actual content instead of path references
• The fix maintains the same directory structure and behavior for symlink environments
• No changes to symlink behavior when supported

Checklist

Required Checks

• Documentation is updated (if applicable)
• Files follow existing naming conventions
• Changes are backwards compatible (if applicable)
• Tests added for new functionality (if applicable)

Required Automated Checks

The following validation commands must pass before merging:

• Markdown linting: npm run lint:md
• Spell checking: npm run spell-check
• Frontmatter validation: npm run lint:frontmatter
• Skill structure validation: npm run validate:skills
• Link validation: npm run lint:md-links
• PowerShell analysis: npm run lint:ps
• Plugin freshness: npm run plugin:generate

Security Considerations

• This PR does not contain any sensitive or NDA information
• Any new dependencies have been reviewed for security issues
• Security-related scripts follow the principle of least privilege

Additional Notes

[WilliamBerryiii]

@ Maintainers - please hold on this until we can fully confirm the backing issue is as described and we're sure of the approach. I'm on a windows box and can test this, but won't have time for a bit. @peterbryntesson .... if you have access to windows bare metal ... this would be a cool one to run to ground to make sure this fix is correct and we can generate these files correctly (e.g. the fake symlinks) without having to run the regenerate plugins in Admin via powershell.

[WilliamBerryiii]

@stablegenius49 - please sign the LCA

[WilliamBerryiii]

@stablegenius49 - I'm going to take over this branch and complete the work here so that you contribution marker remains. I really appreciate you taking a run at this one and your solution is close, but needs some additions. Should have this completed and tested today, but not sure I'll be able to cut a release until next week due to the other changes we've already merged down into main.

[WilliamBerryiii]

We've updated the PR description to align with the current pull request template. All original content has been preserved and relocated into the appropriate template sections. No action needed on your end — though you're welcome to review the updated description and fill in any remaining sections (testing details, checklist confirmations, etc.) at your convenience.

[stablegenius49]

@microsoft-github-policy-service agree

[WilliamBerryiii]

PR Compliance Update — Added the missing (extension) scope to the PR title to align with the project's Conventional Commits convention:

• Before: fix: inline agent content instead of path stubs in packaged plugins
• After: fix(extension): inline agent content instead of path stubs in packaged plugins

The PR body and Fixes #785 reference were already correctly formatted. Thank you for the contribution! 🙏