chore: seal Design Vision v1 and monorepo scaffold

Archive the differentiated YuXinGu product docs, AI engineering system,
design contract, and Go/Vue scaffold. Next execution prioritizes Cece-parity
over early innovation (see .ai/product/STRATEGY.md).

Co-authored-by: Cursor <cursoragent@cursor.com>

.ai/design/platform/website.md

@@ -0,0 +1,44 @@
+# Platform Contract — Website (Desktop / Marketing Web)
+
+Future or secondary surfaces (landing, SEO pages, admin beyond mobile shell).  
+Brand tokens identical to [../design-system.md](../design-system.md).
+
+---
+
+## MUST
+
+- SEO basics: title / description / semantic headings on marketing pages.
+- Keyboard navigation and visible focus for interactive controls.
+- Hover states allowed as **enhancement**; core actions still work without hover.
+- Large screens: may use sidebar, table, multi-column — do not ship desktop-only flows that leave mobile broken if the same app is responsive.
+- Accessibility: contrast, labels, skip/focus order.
+- Admin (`apps/admin-h5`): denser List/Table OK; still use tokens (primary coral, not random admin blue).
+
+---
+
+## MUST NOT
+
+- Purple SaaS gradient landing that ignores 愈心谷 peach/coral brand.
+- Heavy dashboard chrome on consumer marketing hero (see design-system home budget).
+- Medical / 吉凶 claims in SEO copy.
+
+---
+
+## Breakpoints
+
+| Name | Guide |
+|---|---|
+| Mobile | < 768px — follow H5 patterns |
+| Tablet | 768–1024px — adapt columns, keep touch sizes |
+| Desktop | > 1024px — sidebar / multi-column allowed |
+
+Do not merely scale desktop UI down to mobile.
+
+---
+
+## Checklist
+
+- [ ] Tokens + brand voice
+- [ ] Keyboard / focus
+- [ ] Responsive behavior explicit
+- [ ] SEO for public pages