#799: Vim compat 1/9: land the extended Neovim-oracle harness (1,432 cases) with a known-deviation list and make it a CI gate - #808

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