write-spec-full

Write a full specification for a change that spans more than one PR, has a measurement behind it, or has decisions a reviewer will want to argue with. Covers the verbatim ask, measured problem, cited facts, assumptions checked, options with a recommendation, phases where Phase 0 changes no behaviour, test plan, rollback, out-of-scope, and open questions — then stops for sign-off. Use when asked to spec, design, or plan a non-trivial change.