Build and test Python 3.15 wheels with cibuildwheel - #946

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: brettcannon/check-for-changed-files@871d7b8b5917a4f6f06662e2262e8ffc51dff6d1. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/