Comprehensive React component coding guidelines, refactoring principles, and architectural patterns. **CRITICAL**: Focuses on patterns AI commonly fails to implement correctly, especially testability, props control, and component responsibility separation. Reference this skill when implementing or refactoring React components during Phase 2.

GitHub pull request skill. Use when the user asks to open a PR. Produces a short English summary of what changed, and auto-attaches a demo GIF of the new UI by recording screenshots via chrome-devtools MCP.