[RL] Add /pull_weights: engine-side pull of published weights into a host-local checkpoint (sglang-miles) - #30366

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/labeler@v5. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/