Experiment: polyatomic+polyatomic on ic50

FOLD 1/5
GNN Train Loss: 0.8857
RMSE: 0.7223, MAE: 0.5989, R2: 0.0188

FOLD 2/5
GNN Train Loss: 0.9291
RMSE: 0.7255, MAE: 0.5962, R2: -0.0244

FOLD 3/5
GNN Train Loss: 0.8818
RMSE: 1.2848, MAE: 1.0687, R2: -2.2161

FOLD 4/5
GNN Train Loss: 0.8802
RMSE: 0.7078, MAE: 0.5809, R2: -0.0074

FOLD 5/5
GNN Train Loss: 0.8611
RMSE: 0.7062, MAE: 0.5808, R2: -0.0260

====== K-FOLD SUMMARY ======
RMSE: 0.8335  [0.7100, 1.0598]
MAE: 0.6818  [0.5839, 0.8771]
R2: -0.4438  [-1.3360, 0.0012]

★ Using fold 5 model for test inference
RMSE: 0.7223, MAE: 0.5941, R2: -0.0260

====== HELD-OUT TEST METRICS ======
{'rmse': 0.7223211387810183, 'mae': 0.5940642356872559, 'r2': -0.02595531940460205}
Test RMSE: 0.7214  (95 % CI: 0.6656–0.7834)

Test MAE : 0.5949  (95 % CI: 0.5525–0.6428)

Test R²  : -0.0314  (95 % CI: -0.1248–0.0510)