Refactor skill: what it does and how to install it

What it does. Guides gradual refactoring by identifying code smells, applying focused transformations and running tests after each small change. It covers extracting functions and classes, improving type safety, replacing magic values, simplifying conditionals, removing dead code and applying design patterns.

When to use it. For existing code that is hard to understand, maintain or extend, including oversized functions, duplicated logic and weak types. It advises against refactoring untested critical code, stable code that will not change, or changes made without a clear purpose.