onnx.6: sync dev @ 0.25.0-beta.4 (curation dedup fix #1637), prepare 0.25.0-alpha.onnx.6 - #1642

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