task-15(壳层/路由): 实现页面标题与面包屑规则

title-breadcrumb 提供 resolveDocumentTitle('页面 - 数富AI')、updateDocumentTitle
(非浏览器静默)、crumbsForActiveRoute(分组->页面)；AdminLayout 用 watch 同步
document.title 并在层级>1 时渲染 el-breadcrumb。

admin-frontend-vue/src/layout/AdminLayout.vue

@@ -1,5 +1,5 @@
 <script setup lang="ts">
-import { computed, ref } from 'vue'
+import { computed, ref, watch } from 'vue'
 import { useRoute, useRouter } from 'vue-router'
 import { ElMessage } from 'element-plus'
 import { useAdminSessionStore } from '@/stores/admin-session'
@@ -13,6 +13,7 @@ import {
 } from '@/layout/empty-state'
 import GlobalErrorContainer from '@/layout/GlobalErrorContainer.vue'
 import { initialCollapsed, toggleCollapsed, writeCollapsePreference } from '@/layout/sidebar-collapse'
+import { crumbsForActiveRoute, resolveDocumentTitle, updateDocumentTitle } from '@/layout/title-breadcrumb'
 
 const route = useRoute()
 const router = useRouter()
@@ -40,8 +41,15 @@ const openedKeys = computed(() => groupKeysForActive(menuEntries.value, route.pa
 const emptyMenu = computed(() => shouldShowEmptyMenu(menuEntries.value.length > 0, session.loading, session.initialized))
 const pageTitle = computed(() => pageTitleOf(route.meta.title))
 const userVm = computed(() => topbarUserOf(session.user))
+const breadcrumbs = computed(() => crumbsForActiveRoute(session.menuTree, route.path))
 const logoUrl = joinAdminPath('assets', 'logo.jpg')
 
+watch(
+  pageTitle,
+  (title) => updateDocumentTitle(resolveDocumentTitle(title), typeof document !== 'undefined' ? document : null),
+  { immediate: true },
+)
+
 async function signOut() {
   try {
     await session.signOut()
@@ -101,6 +109,9 @@ async function signOut() {
         </div>
       </header>
       <main class="admin-content">
+        <el-breadcrumb v-if="breadcrumbs.length > 1" class="admin-breadcrumb" separator="/">
+          <el-breadcrumb-item v-for="crumb in breadcrumbs" :key="crumb.key">{{ crumb.name }}</el-breadcrumb-item>
+        </el-breadcrumb>
         <GlobalErrorContainer />
         <el-alert v-if="session.error" :title="session.error" type="error" show-icon :closable="false" />
         <el-empty

admin-frontend-vue/src/layout/title-breadcrumb.ts

@@ -0,0 +1,42 @@
+import type { AdminMenuNode } from '../types/admin'
+
+export const ADMIN_BRAND = '数富AI'
+
+/** 文档标题规则：`页面标题 - 数富AI`；无页面标题时仅品牌。 */
+export function resolveDocumentTitle(pageTitle: string, brand: string = ADMIN_BRAND): string {
+  const trimmed = (pageTitle || '').trim()
+  return trimmed ? `${trimmed} - ${brand}` : brand
+}
+
+/** 同步 HTML 文档标题；doc 为空(如非浏览器环境)时静默跳过。 */
+export function updateDocumentTitle(title: string, doc: { title: string } | null | undefined): void {
+  if (doc) doc.title = title
+}
+
+export interface BreadcrumbItem {
+  key: string
+  name: string
+  route?: string
+}
+
+/**
+ * 面包屑规则：在菜单树中定位激活路由，返回“分组 -> 页面”层级（顶层叶子只返回自身）。
+ * 无命中返回空数组，不伪造路径。
+ */
+export function crumbsForActiveRoute(nodes: AdminMenuNode[] | null | undefined, activeRoute: string): BreadcrumbItem[] {
+  for (const node of nodes || []) {
+    if (node.route === activeRoute) return [{ key: node.key, name: node.name, route: node.route }]
+    const children = node.children || []
+    for (const child of children) {
+      if (child.route === activeRoute) {
+        return [
+          { key: node.key, name: node.name },
+          { key: child.key, name: child.name, route: child.route },
+        ]
+      }
+    }
+    const nested = crumbsForActiveRoute(children, activeRoute)
+    if (nested.length) return [{ key: node.key, name: node.name }, ...nested]
+  }
+  return []
+}

admin-frontend-vue/src/styles/main.css

@@ -52,6 +52,7 @@ button, input, textarea, select { font: inherit; }
 .page-error { color: #b91c1c; }
 .not-found { padding: 56px 20px; }
 .global-error-stack { display: flex; flex-direction: column; gap: 10px; margin-bottom: 14px; }
+.admin-breadcrumb { margin-bottom: 14px; }
 
 @media (max-width: 820px) {
   .admin-sidebar { flex-basis: 64px; }