Sample crystal structures with Matra-Genoa for GenBench

GenBench's sample contract: num_samples structures for a formula, a chemical system (Matra-Genoa picks the stoichiometry for each element set) or with no condition at all, each relaxed with ORB v3 and returned as an inline CIF. Duplicates are kept and nothing is saved or published, so a benchmark can call it many times. Usually answers in under a minute. Cite Matra-Genoa: De Breuck et al., npj Comput. Mater. 12, 60 (2026).