Also record the distilled checkpoint filename in metadata.json so both
generators are resolved from metadata by the Earth2Studio wrapper.
Add corrdiff-era5-hrrr-distil: 2-step distilled generator (PDD + almost-fair CRPS post-training, EMA at step 5000) of the corrdiff-era5-hrrr teacher; load with CorrDiffEra5Hrrr.load_model(..., distilled=True); 2-step median RMSE +0.48% / CRPS +0.86% vs the 50-step teacher, 45x cheaper
Update x_pred to the final corrdiff-era5-hrrr model (stage-2 noise-ceiling fine-tune to t_max 0.9999, EMA of the last 22 snapshots; u10m RMSE 1.11 m/s, t2m 0.81 K on the 5 held-out ICs)
Add x_pred/ package: x-prediction rectified-flow DiT weights (EMA at 17.5 Mimg) with metadata, normalization stats, grids and invariants for earth2studio
