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/source.py

@@ -307,6 +307,7 @@ _HEAD = re.compile(
 def _regex_ranges(text: str, language: str) -> tuple[FunctionRange, ...]:
     lines, code = text.splitlines(), _code_lines(text)
     result = []
+    end: int | None
     for index, line in enumerate(code):
         name = declarator_name(line, language)
         if language == "python":