Brummel
6390093f93
load_m1_window collected every bar into an intermediate Vec<M1Parsed> (a full AoS materialization, un-presized so it grew by reallocation) before transpose_m1 copied it again into the SoA columns — ~2x peak load memory plus realloc churn. Transpose each chunk straight into the columns instead, via a new shared M1Columns::extend_from_bars (reserves per chunk for amortized growth). One fewer full copy, halved peak. Behaviour-preserving: the resulting M1Columns is byte-identical and transpose_m1's / load_m1_window's signatures are unchanged. Pinned by a new parity test that needs no live DataServer. closes #78