DFA + residual-branch penalty test: seed=42, lam=0.01
  ep 0: ||h_L||=8.893e+00 ||g_2||=9.934e-04 acc=0.1152
  ep 1: ||h_L||=7.888e+02 ||g_2||=1.141e-05 eval_acc=0.3359 test_acc=0.3353
  ep 10: ||h_L||=7.251e+03 ||g_2||=2.304e-06 eval_acc=0.3662 test_acc=0.3517
  ep 20: ||h_L||=1.137e+04 ||g_2||=1.814e-06 eval_acc=0.3730 test_acc=0.3649
  ep 30: ||h_L||=1.216e+04 ||g_2||=1.757e-06 eval_acc=0.3750 test_acc=0.3593

FINAL test acc: 0.3593
Compare to:
  DFA-vanilla (3-seed mean):    0.308
  DFA-shallow (3-seed mean):    0.349
  DFA-frozen (3-seed mean):     0.349
  BP-trainable (3-seed mean):   0.609
Saved results/dfa_pen_short/dfa_pen_lam0.01_s42.json
Saved results/dfa_pen_short/dfa_pen_lam0.01_s42.pt