Write a comprehensive implementation guide for the {{pattern}} pattern in {{framework}} at {{complexity}} complexity level. Use a {{tone}} tone. The guide must include: Pattern Overview, Implementation Architecture (project setup, foundation, business logic, UI integration, side effects), Real-World Example (User Profile feature), Testing the Pattern, Common Mistakes (7 items), and Performance Considerations. Maximum 1800 words. Every code example must be valid TypeScript with type annotations. Use precise technical terminology. Document assumptions and provide error handling.