Swift Format Style

If you're still using DateFormatter, NumberFormatter, or String(format:) in Swift projects, this skill will hunt them down and replace them with modern FormatStyle APIs. It reviews your code against a set of anti-patterns and rewrites formatting logic to use .formatted() and proper FormatStyle types for numbers, dates, durations, measurements, lists, and more. The skill knows the difference between simple cases where .formatted() works and complex scenarios where you need explicit FormatStyle configuration. It also catches SwiftUI-specific issues like using string interpolation in Text views instead of the format parameter. Targets iOS 15+ and knows which features require iOS 16+. Think of it as a linter and refactoring tool rolled into one, specifically for Apple's formatting APIs.