Misc. fixes - #980

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, leafo/gh-actions-lua@v9, leafo/gh-actions-luarocks@v4. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

gh-actions-lua: Failed to save to cache (continuing anyway): ReserveCacheError: Unable to reserve cache with key lua:5.1.5:linux:x64:, another job may be creating this cache.