Change: the solver's per-step records are CSV files (Continuity_Metrics.csv, solution_convergence.csv, Runtime_Memory.csv, the momentum and Poisson histories, ProfilingSummary_*.csv). The particle step counts, occupied cells included, are in search_metrics.csv. The logged maximum-divergence location is the owning rank's, and the Poisson true residual is computed only when pic_true_residual asks for it.