Refactor DSPy-driven optimization flow with coordinator-based orchestration - #48

Node.js 20 is deprecated. The following actions target Node.js 20 but are being forced to run on Node.js 24: actions/checkout@692973e3d937129bcbf40652eb9f2f61becf3332, actions/upload-artifact@0b2256b8c012f0828dc542b3febcab082c67f72b. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/