fix(types): mypy clean again over src; stub-less libraries and the benchmark imports handled in pyproject

66 errors had accumulated in src since the last green run (the hunt modules of groups 4-6, stats, candidates,
runner). Codex typed them without behaviour change; the 17 inline import-untyped ignores it added are replaced by
one override for dspy, pandas, statsmodels and scikit-learn, and the hunt package's lazy imports of benchmarks/
(never type-checked, not in files) are followed silently so src stays strict against their signatures.

Co-Authored-By: Claude Fable 5.1 <[email protected]>

src/openultrasast/hunt/ablation.py

@@ -190,7 +190,7 @@ def run(
     if table.digest() != manifest.table_digest:
         raise ValueError("table digest does not match registration")
     runner.refuse_pilot(Path(pool_manifest_path), pilot_report=False)
-    folds: dict[str, tuple[str, int]] = {}
+    folds: dict[str, tuple[str, int | None]] = {}
     for row in table.rows:
         key, value = row["change_id"], (row["repo"], row.get("fold"))
         if key in folds and folds[key] != value: