- HNSW (Ubuntu): add libopenblas-dev for BLAS requirements
- DiskANN (Ubuntu): keep MKL, remove redundant pkg-config (HNSW already has it)
- DiskANN (macOS): add protobuf for build requirements
- Both: ensure patchelf for auditwheel on Linux
This avoids OpenBLAS/MKL conflicts by using them in separate jobs