docs(proxy-reflect): add comprehensive Proxy and Reflect concept page with tests

- Cover all 13 proxy handler traps with detailed explanations
- Include practical patterns: validation, observable data, access control, logging
- Add revocable proxies and limitations sections (Map/Set internal slots, private fields)
- Create 23 passing tests for all code examples
- Add curated resources: 3 MDN refs, 4 articles, 3 videos
- SEO optimized with question hook, featured snippet definition, internal linking