refactoringlisted

# Refactoring - **Duplication** → Extract function/class - **Long methods / mixed abstraction** → Break into private helpers; see [levels-of-abstraction](../levels-of-abstraction/SKILL.md) for the smells (keep tests on public interface) - **Shallow modules** → Combine or deepen - **Feature envy** → Move logic to where data lives - **Primitive obsession** → Introduce value objects - **Existing code** the new code reveals as problematic