claude
d63619bd0e
Add FrozenHoldoutSplit with deterministic 15% ratio using dedicated hash seed. Produces frozen/dev partition with SplitGroup-aware leakage prevention — all contrastive variants of one seed stay in the same split. Add GroupedCVFolds for k-fold grouped cross-validation on the development pool. Each fold preserves split_group boundaries; every example appears in exactly one eval set across all folds. Tests verify determinism (same split → same hash), no split_group leakage across frozen/dev, route coverage in both pools, fold completeness, and grouped CV coverage.