docs(macos): installing the unsigned build on macOS 14 / 15+, and the minimum macOS version (#1594, #1591) - #1706

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. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/