fix(planner): dataset_plan_analysis must say how to LOAD the dataset

style: apply ruff lint --fix + ruff format across the tree

feat(loveless): integrate biodata-registry 0.1.8 sc datasets (Path P by modality)

feat(loveless): ADR-0006 #6 — h5ad source type + Path P loading plan

ADR-0001 Phase 1, step 3 (T4): dataset_get_integration_plan wrapper + 0.1.2 re-pin

Split dataset_tools.py (1709) into a package preserving the public API