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/review.md

@@ -0,0 +1,40 @@
+# AI Self-Review — mandatory before claiming Done
+
+After coding, check every item. Output a Review block.
+
+## Checklist
+
+| Area | Ask |
+|---|---|
+| Architecture | Layers respected? No Handler→DB? |
+| Naming | Consistent domain terms? |
+| Performance | Obvious N+1 / unbounded lists? |
+| Security | AuthZ, validation, no secrets? |
+| Readability | Files ≤400, funcs ≤50? |
+| Error handling | Wrapped errors / user-safe messages? |
+| Logging | Structured, no PII spam? |
+| Test | Critical path covered or smoke listed? |
+| Deployment | Migration / health / env noted if needed? |
+| Docs | OpenAPI / PRD touch if public behavior changed? |
+| Design | UI change? Tokens + catalog + platform contract followed? |
+| Scope | No unrelated files modified? |
+
+## Output format (required)
+
+```
+## Review
+- Architecture: PASS | FAIL — <note>
+- Naming: PASS | FAIL — <note>
+- Performance: PASS | FAIL — <note>
+- Security: PASS | FAIL — <note>
+- Readability: PASS | FAIL — <note>
+- Error handling: PASS | FAIL — <note>
+- Logging: PASS | FAIL — <note>
+- Test: PASS | FAIL — <note>
+- Deployment: PASS | FAIL — <note>
+- Docs: PASS | FAIL — <note>
+- Design: PASS | FAIL | N/A — <note>
+- Scope: PASS | FAIL — <note>
+```
+
+Any FAIL → fix before finishing. Do not hide FAILs.