Owner class_structure; base f4ef0715bbe2f4890b3dcea034757ef0c823053a. Read-only PR279 3f136908426167ff97888a6ae8b89087223509e6. Write only this directory. No Git mutation, paid compute, or heavy runs. Each exact experiment is capped at 20 CPU seconds, single process. Goal: test whether genus structure yields a useful filter or independent completeness audit, distinct from a larger class-number cutoff. Success requires exact assumptions, proof versus finite evidence separation, falsification controls and reproducible artifacts. No novelty from mere absence in a search. Outcome and next discriminating check in RESULTS.md.