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>

packages/types/package.json

@@ -0,0 +1,11 @@
+{
+  "name": "@yuxingu/types",
+  "version": "0.1.0",
+  "private": true,
+  "type": "module",
+  "main": "./src/index.ts",
+  "types": "./src/index.ts",
+  "exports": {
+    ".": "./src/index.ts"
+  }
+}

packages/types/src/index.ts

@@ -0,0 +1,25 @@
+/** Unified API envelope from apps/api. */
+export interface ApiResponse<T = unknown> {
+  code: number
+  message: string
+  data?: T
+}
+
+/** User profile used by decode / relation features. */
+export interface Profile {
+  id: string
+  label: string
+  year: number
+  month: number
+  day: number
+  relation: 'self' | 'other'
+}
+
+/** Minimal scale list item. */
+export interface ScaleSummary {
+  slug: string
+  name: string
+  category: string
+  questionCount: number
+  description?: string
+}