- Add .themed class as shared selector for both shop and preview
- Move visual/behavioral styles from .preview-frame to .themed
- Keep .preview-frame only for CSS variable switching (editor live preview)
- Update CSSGenerator to target .themed instead of .shop-root
- Refactor CSS files to use native CSS nesting syntax
- Update tests to reflect new class structure
This improves maintainability by:
- Eliminating duplicate selectors (.shop-root + .preview-frame)
- Using modern CSS nesting (94%+ browser support)
- Clear separation: .preview-frame = vars, .themed = styles
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>