refactor-masterlisted

# refactor-master — change shape without changing behavior ## When to use this skill Trigger when the user wants the code reorganized but expects the same outputs. Strong signals: - "refactor this", "clean up", "split", "decompose", "extract" - "this file is 1200 lines, help" - "make this readable" - "pull the logic out of the React component" Do *not* trigger for: behavior changes (that's a feature, not a refactor), performance work (use `perf-hunter`), or a one-line rename (just do it). ## The output contract Refactors that: 1. **Preserve behavior** — every existing test still passes. If there are no tests, add a characterization test first (see step 2). 2. **Land in small steps** — each commit is independently reviewable and reverts cleanly. 3. **Reduce one specific kind of complexity** — say which one upfront (cyclomatic, depth, length, coupling, naming) and measure before/after. 4. **Don't leak new abstractions** — no `BaseFooFactoryProviderInterface` unless there are at least three concrete implementations that need it. ## Workflow ### 1 — Diagnose Read the target. Name the *specific* smell, out loud, before touching: - **Length**: function/file is too long → extract by responsibility - **Depth**: too many levels of nesting → early returns, guard clauses, or extract inner blocks - **Repetition**: same pattern 3+ times → extract a helper - **God object**: one class doing too many things → split by axis of change - **Tangled side effects**: pure logic interwove