build!: drop automated PyPI/npm release workflows; document release policy - #71

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683, actions/github-script@v7, astral-sh/setup-uv@bd01e18f51369d5a26f1651c3cb451d3417e3bba. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/