feat: MenuNav layer for the SummerCMS menu API

- typed client and useMenu/useMenuApi (SSR, menu:<code>:<locale> key,
  server and public bases, x-forwarded-for forwarded also on cached renders)
- MenuNav and recursive MenuNavItem: WAI disclosure navigation, URL
  allowlist with a text fallback, rel on _blank, active link and trail,
  mobile toggle, Esc / focus-out / outside pointer / route change closing
- menu tokens and base CSS, README
- node tests (link rules, client, server-rendered NavItem) and a playground
  SSR smoke against a fixture API

package.json

@@ -0,0 +1,25 @@
+{
+  "name": "vue-menu-layer",
+  "version": "0.1.0",
+  "private": true,
+  "type": "module",
+  "main": "./nuxt.config.ts",
+  "scripts": {
+    "dev": "nuxi dev .playground",
+    "build:playground": "nuxt build .playground",
+    "test": "node --test --test-reporter=tap tests/*.test.ts",
+    "dev:prepare": "nuxt prepare .playground",
+    "smoke:ssr": "node testing/smoke-ssr.mjs --output .playground/.output --fixtures testing/fixtures --expect testing/expect.txt"
+  },
+  "engines": {
+    "node": ">=22.18"
+  },
+  "peerDependencies": {
+    "nuxt": "4.4.8"
+  },
+  "devDependencies": {
+    "nuxt": "4.4.8",
+    "typescript": "5.9.3",
+    "vue": "3.5.35"
+  }
+}