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>

package.json

@@ -0,0 +1,14 @@
+{
+  "name": "yuxingu",
+  "private": true,
+  "workspaces": [
+    "apps/user-h5",
+    "apps/admin-h5",
+    "packages/*"
+  ],
+  "scripts": {
+    "dev:h5": "npm run dev -w @yuxingu/user-h5",
+    "build:h5": "npm run build -w @yuxingu/user-h5",
+    "dev:api": "cd apps/api && go run ./cmd/server"
+  }
+}