Fix Stream.closeWritable to await close completion - #133

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/cache/restore@v4, actions/cache/save@v4, actions/checkout@v4, DeterminateSystems/nix-installer-action@90bb610b90bf290cad97484ba341453bd1cbefea. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/