BRICK stage 3. Reduces complexity and duplication in code that is already green, and adds property-based tests, without changing behaviour.
Every test green before is green after. The suite is the safety net, so a refactor that requires editing a test is not a refactor — it is a behaviour change, and it stops.
Adds property tests where a calculation has a law worth stating. Harness-layer BRICK stage skill with clean stratified disclosure. Always activate together with `code-writer` and the disclosed language skills.
