fix: allow release reruns after publish

[andyWang1688]

Summary

• allow the release workflow to skip PyPI upload on reruns when the version already exists and the GitHub Release is already present
• keep explicit manual recovery support for cases where PyPI publish succeeded before GitHub Release creation
• cover the rerun decision logic with regression tests in release metadata helpers

Test Plan

• actionlint
• PYTHONPATH=. python -m unittest tests.test_release_metadata -v
• PYTHONPATH=. python -m unittest discover -s tests