3-column 3-row plot:
  rows: ||h_L||, ||g_L||, test accuracy
  cols: ResMLP (with LN) | ViT-Mini (cls + LN) | StudentNet (no LN)

BP and DFA trajectories overlaid. Floor threshold drawn on the ||g_L||
row. Visualizes the cross-architecture causal control: with-LN
architectures both show ||g_L|| collapse below 1e-7 (DFA hits the floor
within 5 epochs); without-LN architecture shows ||g_L|| stays in the
healthy regime even though ||h_L|| still grows (catastrophic vs mild).