retrain model_6h: new val/test split (val>=2026-01-01, test>=2026-04-01)

retrain model_12h: new val/test split (val>=2026-01-01, test>=2026-04-01)

promote model_6h: test.mean_pinball inf -> 0.00891

promote model_12h: test.mean_pinball inf -> 0.00883

initial commit