(fix): temporary filename is non-random, causing bad state and the killthreads fedora flake - #10

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@c85c95e3d7251135ab7dc9ce3241c5835cc595a9. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/