qa-refactoring

# QA Refactoring Safety Use this skill to refactor safely: preserve behavior, reduce risk, and keep CI green while improving maintainability and delivery speed. Defaults: baseline first, smallest safe step next, and proof via tests/contracts/observability instead of intuition. ## Quick Start (10 Minutes) - If key context is missing, ask for: what must not change (invariants), risk level (money/auth/migrations/concurrency), deployment constraints, and the smallest boundary that can be protected by tests. - Confirm baseline: `main` green; reproduce the behavior you must preserve. - Choose a boundary: API surface, module boundary, DB boundary, or request handler. - Add a safety net: characterization/contract/integration tests at that boundary. - Refactor in micro-steps: one behavior-preserving change per commit/PR chunk. - Prove: run the smallest relevant suite locally, then full CI; keep failures deterministic. ## Core QA (Default) ### Safe Refactor Loop (Behavior First) - Establish baseline: get `main` green; reproduce the behavior you must preserve. - Define invariants: inputs/outputs, error modes, permissions, data shape, performance budgets. - Add a safety net: write characterization/contract/integration tests around the boundary you will touch. - Create seams: introduce injection points/adapters to isolate side effects and external dependencies. - Refactor in micro-steps: one behavior-preserving change at a time; keep diffs reviewable. - Prove: run the smallest rele...