Loads spherically-averaged neutral-atom density matrices in a fixed minimal reference basis (STO-3G, Cartesian) from the OpenQP data file (basis_sets/minao_sto3g.dat, generated offline by tools/minao/generate_minao_data.py from PySCF's atomic HF densities). These are superposed block-diagonally and projected onto the target basis to form the MINAO initial guess.