Improve Native AOT command migration skill

[JeremyKuhne]

Summary

• expand the Native AOT command skill into a self-contained author and reviewer workflow
• document eligibility, fallback commit points, closure ownership, SDK-root handling, and proof boundaries
• add a validation ladder covering managed checks, Native AOT publish, native tests, dn parity, separated layouts, and size evidence
• clarify that AotSourceFiles.props owns source and resources while AotDependencies.props owns package and project dependencies

Validation

• ./.dotnet/dotnet.exe .github/skills/ValidateSkill.cs .github/skills/add-dotnet-aot-command
• git diff --check

No product tests were run because this changes agent guidance and an MSBuild comment only.

[azure-pipelines]

Azure Pipelines:
Successfully started running 2 pipeline(s).
1 pipeline(s) were filtered out due to trigger conditions.
There may be pipelines that require an authorized user to comment /azp run to run.

[Copilot]

Pull request overview

This PR updates repository guidance for migrating or reviewing dotnet CLI commands in the Native AOT CLI (src/Cli/dotnet-aot) by expanding the add-dotnet-aot-command skill into a more complete author + reviewer workflow, and clarifying closure ownership boundaries between AotSourceFiles.props and AotDependencies.props.

Changes:

• Expanded .github/skills/add-dotnet-aot-command/SKILL.md into a structured workflow (contracts, author/reviewer checklists, validation ladder, and evidence expectations).
• Clarified that AotSourceFiles.props owns linked sources/resources, while package/project dependency closure belongs in AotDependencies.props.
• Added more explicit validation/evidence guidance (clean builds after closure changes, Native AOT publish, native test runs, dn parity, separated layout, and size reporting).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/Cli/dotnet-aot/AotSourceFiles.props	Updates the header guidance to direct dependency additions to AotDependencies.props, reinforcing the intended closure split.
.github/skills/add-dotnet-aot-command/SKILL.md	Rewrites and expands the skill into a self-contained migration/review workflow with contracts, validation ladder, and evidence requirements.