Merge branch 'phase2-secondary-prediction' into 4-prototype-a-mixture-of-experts-routing-tree-architecture

Brings in the rollout-validation fixes developed alongside Phase 2
(exact e_sec budget rescaling in decode_secondaries, filtering
synthetic termination rows out of load_rollout_vs_truth, Tier 4 truth
overlay, --energy-gev support in dwarf make-root) and reconciles them
with this branch's mixture-of-experts routing work: build_features/
build_models/dataset plumbing keep the ProcessRouter's proc_map/
proc_idx threading, and create_root_files.py's job_seed folds in both
the per-job seed derivation and the new energy_gev component.

giant/data/loader.py

@@ -60,9 +60,7 @@ def _pad_list_col_int(series: pd.Series, K: int, fill: int = 0) -> np.ndarray:
     return out
 
 
-def _pad_dir_col(
-    dx: pd.Series, dy: pd.Series, dz: pd.Series, K: int
-) -> np.ndarray:
+def _pad_dir_col(dx: pd.Series, dy: pd.Series, dz: pd.Series, K: int) -> np.ndarray:
     """Pad three list-valued direction columns → (N, K, 3) float32.
 
     Padding direction defaults to (0,0,1) (forward) so it is a valid unit vector.