feat(client): multiplex HTTP/2 requests and clear connections - #13

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, DeterminateSystems/nix-installer-action@v20. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/