Momentic spec-driven development

Write the expected product behavior as Momentic tests before implementing it. The tests define the contract; do not make the tests fit the implementation.

Non-negotiable sequence

1. Read repository guidance, momentic.config.yaml, and nearby tests and modules.
2. Identify and report the exact Momentic tests expected to be affected.
3. Create or modify those tests before changing product code.
4. Review the test diff as a product specification.
5. Only then implement the product change.
6. Use fast code-level checks while implementing; do not run Momentic after every edit or commit.
7. At a durable end-to-end checkpoint, prepare the required test state, enable the affected tests that should now pass, and ask whether to run the smallest affected set.