exp: E28 - under DPPO, dppo-policy learns HalfCheetah and climbs Hopper/Walker2d; fpo-policy does not move - #63

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, astral-sh/setup-uv@v5. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/