DFA + residual-branch penalty test: seed=42, lam=0.0001
  ep 0: ||h_L||=8.893e+00 ||g_2||=9.934e-04 acc=0.1152
  ep 1: ||h_L||=3.544e+03 ||g_2||=2.682e-06 eval_acc=0.3154 test_acc=0.3127
  ep 10: ||h_L||=1.654e+04 ||g_2||=7.706e-07 eval_acc=0.3496 test_acc=0.3479
  ep 20: ||h_L||=2.248e+04 ||g_2||=6.429e-07 eval_acc=0.3633 test_acc=0.3616
  ep 30: ||h_L||=2.365e+04 ||g_2||=6.276e-07 eval_acc=0.3643 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_lam0.0001_s42.json
Saved results/dfa_pen_short/dfa_pen_lam0.0001_s42.pt