refactor

# Refactor Improve code structure without changing external behavior. ## Process 1. **Understand** — Read all related code, run existing tests 2. **Plan** — Identify what to change and why 3. **Execute** — Make changes incrementally 4. **Verify** — Run tests after each change ## Common Refactoring Patterns ### Extract - Long function → smaller focused functions - Repeated code → shared helper - Magic numbers → named constants ### Simplify - Deep nesting → early returns / guard clauses - Complex conditionals → descriptive functions - Large classes → smaller focused classes ### Rename - Unclear names → descriptive names - Inconsistent naming → consistent conventions ### Reorganize - Related functions scattered → grouped in modules - Circular dependencies → dependency inversion ## Rules - Never change behavior — tests must pass before and after - One refactoring type per commit - If tests don't exist, write them first - Don't refactor and add features in the same change