Unified entry point for Stitch design work. Handles prompt enhancement (UI/UX keywords, atmosphere), design system synthesis (.stitch/DESIGN.md), and high-fidelity screen generation/editing via Stitch MCP.

响应指南 - 简洁响应 + 按需提示词增强。核心铁律：简洁优先，保真原意，禁止扩展范围。