Alembic/Flask-Migrate revisions, Django migrations, and protobuf/OpenAPI
generated files produce hundreds of degree-1 rationale nodes labeled as
'possible documentation gaps'. Their module docstrings are revision
annotations or boilerplate, not architectural rationale.
- Add _is_autogenerated_python() in extract.py detecting Alembic, Django
migrations, and generic DO-NOT-EDIT markers; skip module docstring only
- Function/class docstrings inside those files still extracted as normal
- report.py: exclude file_type=rationale nodes from isolated-node gaps
section — rationale nodes are degree-1 by construction; flagging them
as missing edges was always wrong
- 5 new tests covering Alembic, Django, protobuf, false-positive guard,
and function-docstring passthrough