Split registry publishing to separate workflows

[MathieuGilbert]

Is this PR a bug fix, new feature, or security update?

The last change didn't deploy to either registry. We haven't deployed an update in over a year, so some permissions may have changed since then.

Otherwise, it's possible the OIDC is being applied to both calls, breaking the GitHub publish. I'm not sure what's wrong with the npmjs OIDC.

Please describe this pull request:

Split publish to GitHub workflow, so it doesn't try to use the same auth for both.

PR Review Checklist

• I have passing tests run via npm run test with a 100% coverage threshold
• I have updated the version in package.json
• I have updated any relevant documentation in README.md, .github, etc.
• I have not included any secret values or links to internal AMA URLs in my commits or PR message