ci: break out publish job

[michaelfaith]

PR Checklist

• Addresses an existing open issue: fixes #000
• That issue was marked as status: accepting prs
• Steps in CONTRIBUTING.md were taken

Overview

This change breaks the publish portion of our release flow into its own job (separate from the release-please pr management), so that we can re-run it if needed (e.g. npm publishing error).

The job sequence is now release_please -> publish (if release created) -> post_release

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.14%. Comparing base (1f795f8) to head (1f3f938).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1545   +/-   ##
=======================================
  Coverage   97.14%   97.14%           
=======================================
  Files          28       28           
  Lines         596      596           
  Branches      175      175           
=======================================
  Hits          579      579           
  Misses          2        2           
  Partials       15       15           

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