feat: add Cohen's Kappa metric to classifier evaluation and output

main.py

@@ -95,6 +95,7 @@ def main():
     print(f"Training samples: {metrics['train_samples']}")
     print(f"Validation samples: {metrics['val_samples']}")
     print(f"Accuracy: {metrics['accuracy']:.2%}")
+    print(f"Cohen's Kappa: {metrics['kappa']:.4f}")
     print(f"Classes: {metrics['classes']}")
     print()