Predict the magnetic ordering temperature (Curie, or Néel for antiferromagnets) from classical Heisenberg Monte Carlo on TB2J exchange couplings. Tc_K is the susceptibility peak in a supercell twice the longest kept coupling wide; Tc_mean_field_K is the mean-field upper bound. Also returns the magnetization curve and reference_ordering_overlap: near 1 when the couplings favor the SCF's own collinear order. Below 0.5 the response carries a warning: Tc belongs to a different ordering, because either the SCF started from the wrong one (check with /dft/magnetic/ordering) or a rigid-spin Heisenberg model cannot describe the magnet (e.g. L1₀ FePt, whose ferromagnetism is mediated by induced Pt moments). Shares its calculation with /dft/magnetic/exchange at the same settings. Key descriptor for permanent-magnet screening alongside MAE.