Fix Python reference leaks in message and native helpers - #256

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@v4, actions/download-artifact@v4, actions/setup-python@v5, actions/upload-artifact@v4. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

cibuildwheel: Bumping MACOSX_DEPLOYMENT_TARGET (10.13) to the minimum required (10.15).

cibuildwheel: Invalid skip selector: 'pp*'. This selector matches a group that wasn't enabled. Enable it using the `enable` option or remove this selector. This selector will have no effect.

cibuildwheel: Invalid skip selector: 'cp38-*'. cibuildwheel 4.x no longer supports Python < 3.9. Please use the 3.x series or update `skip`. This selector will have no effect.

cibuildwheel: Invalid skip selector: 'cp37-*'. cibuildwheel 4.x no longer supports Python < 3.9. Please use the 2.x series or update `skip`. This selector will have no effect.