Introduce agentic-workflow to manage and update CsWin32 Package

[DeagleGross]

CsWin32 Package is a good candidate to test out agentic-workflow updates, since it was not updated for a long time (see #65516)

I am proposing to use an agentic-workflow, which will periodically:

1. check if there is a newer version on NuGet, and update if there is one
2. verify if there are possibilities to improve APIs or remove our workarounds (like hardcoding enum values - we have to do it sometimes when API is already there and we are implementing a feature, but package did not obtain new members yet).

It should not be a burden to review small PRs making a small change, but will keep codebase up to date.

Test runs:

• Agentic workflow
• PR produced by workflow

Closes #63686

[Copilot]

Pull request overview

This pull request introduces an agentic workflow to automate the monthly maintenance of the Microsoft.Windows.CsWin32 package dependency. The workflow will check for new stable package versions, update the version in eng/Versions.props if needed, and systematically search for and remove workarounds that were added for missing Win32 APIs, enum values, or types that are now available in newer CsWin32 releases.

Changes:

• Adds a monthly scheduled workflow using the agentic workflow framework (.md definition + compiled .lock.yml)
• Configures safe-inputs tool to query NuGet API for latest package versions
• Documents comprehensive patterns for identifying CsWin32 workarounds (hardcoded enum casts, manual P/Invoke declarations, manual struct definitions, TODO comments)
• Marks generated .lock.yml files as linguist-generated in .gitattributes

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
.github/workflows/cswin32-update.md	Workflow definition with frontmatter configuration, documentation, and detailed instructions for version checking, building, and workaround cleanup
.github/workflows/cswin32-update.lock.yml	Auto-generated GitHub Actions workflow file compiled from the .md definition (contains typo from source)
.github/aw/actions-lock.json	Action version pinning for actions/github-script@v8 and gh-aw/actions/setup@v0.45.5
.gitattributes	Marks .github/workflows/*.lock.yml as linguist-generated with merge strategy 'ours'

[dotnet-policy-service]

Hey @dotnet/aspnet-build, looks like this PR is something you want to take a look at.

[dotnet-policy-service]

Looks like this PR hasn't been active for some time and the codebase could have been changed in the meantime.
To make sure no conflicting changes have occurred, please rerun validation before merging. You can do this by leaving an /azp run comment here (requires commit rights), or by simply closing and reopening.