rc13
docs: tighten comments codebase-wide — detail lives in secsec-*.md Module docs compressed to short summaries with § pointers; fn docs cut to 1-3 lines keeping MUST/safety contracts; inline origin-story blocks reduced to the constraint they guard. Also drops a stale 'genesis generation only' claim on open_repo (it peels any generation). Comments/docs only — no behavior change. 260 tests, clippy -D warnings, fmt, and KAT vectors all green.