Feature/hierarchical bucketpq - #82

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, hendrikmuhs/ccache-action@v1.2. For more information see: https://github.blog/changelog/2025-09-19-deprecation-of-node-20-on-github-actions-runners/

llvm@20 was installed but not linked because llvm@18 and llvm@22 are already installed. To link this version, run: brew link llvm@20