Stable checkpoint — invariants 2 + 6 (cascade) + smoke flow Cumulative since stable-py-v0.6.5 : - invariant 2 (stock non-negativity) : 3 Hypothesis tests on Pydantic boundary - invariant 6 (cascade safety) : 3 pytest-asyncio + Testcontainers Postgres tests - api-smoke.sh : Order/Product/OrderLine E2E flow (POST + GET + DELETE cascade) - 6/6 ADR-0059 invariants now covered cross-language Post-merge main pipeline #2480774420 green at 20:02.