v0.0.6: ci: bump actions to Node.js 24 releases and fix gh release --repo

actions/checkout v4, setup-dotnet v4, upload-artifact v4, and
download-artifact v4 still ship Node.js 20; bump to the latest majors
that run on Node.js 24 (checkout v6, setup-dotnet v5, upload-artifact
v6, download-artifact v7) to clear the deprecation warning.

The release job didn't check out the repo, so gh release create
couldn't infer the repository and failed with "not a git repository".
Pass --repo ${{ github.repository }} explicitly instead of adding a
checkout step, since the job only needs the downloaded artifacts.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>