Fix stable CI publish job being skipped

[JE-Chen]

Summary

• Publish job in stable.yml was gated on refs/heads/stable, but the repo only has main — every push silently skipped the release step.
• Retarget the condition and the version-bump push at main so merges into main actually publish to PyPI and cut a GitHub release.

Test plan

• Merge this PR and confirm the publish job runs (instead of being skipped) on the resulting push to main.
• Verify the version bump commit + tag land on main and the new release appears on PyPI / GitHub Releases.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

Results:
0 new issues

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