Update winapp cli skill based on new winapp CLI 0.2.0 release

[alvinashcraft]

Pull Request Checklist

• I have read and followed the CONTRIBUTING.md guidelines.
• My contribution adds a new instruction, prompt, agent, skill, or workflow file in the correct directory.
• The file follows the required naming convention.
• The content is clearly structured and follows the example format.
• I have tested my instructions, prompt, agent, skill, or workflow with GitHub Copilot.
• I have run npm start and verified that README.md is up to date.

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Description

The winapp CLI was updated to a new preview release over the weekend - v0.2.0. I'm updating the corresponding skill with the latest features and breaking changes.

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Type of Contribution

• New instruction file.
• New prompt file.
• New agent file.
• New plugin.
• New skill file.
• New agentic workflow.
• Update to existing instruction, prompt, agent, plugin, skill, or workflow.
• Other (please specify):

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Additional Notes

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By submitting this pull request, I confirm that my contribution abides by the Code of Conduct and will be licensed under the MIT License.

[Copilot]

Pull request overview

This PR updates the winapp-cli skill to reflect the breaking changes and new features introduced in winapp CLI v0.2.0. The key change is that winapp init no longer auto-generates a development certificate, requiring an explicit winapp cert generate step. Two new capabilities — Microsoft Store integration (winapp store) and external catalog creation (winapp create-external-catalog) — are documented, along with .NET (csproj) project support details.

Changes:

• Documents v0.2.0 breaking change: winapp init no longer auto-generates a certificate; explicit winapp cert generate is now required
• Adds documentation for two new capabilities: Microsoft Store integration and external catalog creation
• Adds .NET (csproj) NuGet-based project support and associated limitations/notes

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
skills/winapp-cli/SKILL.md	Core skill file updated with new sections (8 & 9), revised guidelines, new usage patterns, limitations, and a new reference link for .NET projects
docs/README.skills.md	Mirrors the updated description field from SKILL.md frontmatter