task-12(壳层/路由): 实现路由级错误页面(404 兜底)

新增 src/pages/error/NotFoundPage.vue（el-result + 返回首页），router 在业务路由
之后注册 :pathMatch(.*)* 兜底（无 menuKey，不参与权限门禁），保留壳层 chrome；
main.css 增加 .not-found 布局。

admin-frontend-vue/tests/task-12.test.ts

@@ -0,0 +1,71 @@
+import test from 'node:test'
+import assert from 'node:assert/strict'
+import { existsSync } from 'node:fs'
+import { join } from 'node:path'
+import { readSource, occurrences } from './helpers.ts'
+import { adminPages } from '../src/router/routes.ts'
+
+const ROUTER = 'src/router/index.ts'
+const NOT_FOUND = 'src/pages/error/NotFoundPage.vue'
+
+test('test_task_012_route_error_page_normal_primary_path', () => {
+  // 正常主路径：未知路径注册到路由级错误页兜底。
+  const router = readSource(ROUTER)
+  assert.match(router, /path:\s*':pathMatch\(\.\*\)\*'/)
+  assert.match(router, /NotFoundPage/)
+  assert.match(router, /页面不存在/)
+})
+
+test('test_task_012_route_error_page_normal_variant_input', () => {
+  // 正常变体：错误页在 AdminLayout children 内，保留壳层 chrome。
+  const router = readSource(ROUTER)
+  const catchAllIndex = router.indexOf(':pathMatch(.*)*')
+  const registryIndex = router.indexOf('adminRouteRecords.map')
+  assert.ok(catchAllIndex > registryIndex, 'catch-all 应在业务路由之后注册')
+  assert.match(router, /path: '\/',/)
+})
+
+test('test_task_012_route_error_page_normal_repeated_operation_is_idempotent', () => {
+  // 正常重复：错误页注册不重复追加。
+  const first = readSource(ROUTER)
+  assert.equal(occurrences(first, ':pathMatch(.*)*'), 1)
+})
+
+test('test_task_012_route_error_page_boundary_empty_input', () => {
+  // 边界空值：错误页文件存在，且不进入业务路由注册表。
+  assert.equal(existsSync(join(process.cwd(), NOT_FOUND)), true)
+  assert.equal(adminPages.length, 3, '错误页不应计入业务路由')
+})
+
+test('test_task_012_route_error_page_boundary_single_item', () => {
+  // 边界单元素：错误页是单一 Vue 页面组件。
+  const source = readSource(NOT_FOUND)
+  assert.equal(occurrences(source, '<template>'), 1)
+  assert.match(source, /el-result/)
+})
+
+test('test_task_012_route_error_page_boundary_limit_or_missing_field', () => {
+  // 边界上限：catch-all 不参与菜单权限门禁（无 menuKey）。
+  const router = readSource(ROUTER)
+  const tail = router.slice(router.indexOf('component: NotFoundPage'))
+  assert.equal(tail.slice(0, 80).includes('menuKey'), false, '错误页不应带菜单 key')
+})
+
+test('test_task_012_route_error_page_invalid_input_rejected', () => {
+  // 异常输入：深层未知路径也能被通配兜底，且提供返回首页动作。
+  const router = readSource(ROUTER)
+  assert.match(router, /:pathMatch\(\.\*\)\*/, '通配需覆盖多段未知路径')
+  const page = readSource(NOT_FOUND)
+  assert.match(page, /router\.replace\('\/'\)/)
+})
+
+test('test_task_012_route_error_page_dependency_failure_returns_actionable_message', () => {
+  // 依赖失败：标题/样式/返回动作齐全，加载失败有明确入口。
+  const page = readSource(NOT_FOUND)
+  assert.match(page, /返回首页/)
+  assert.match(page, /404/)
+  const css = readSource('src/styles/main.css')
+  assert.match(css, /\.not-found/)
+  const router = readSource(ROUTER)
+  assert.match(router, /meta: \{ title: '页面不存在' \}/)
+})