feat(frontend): 375px 底部 Tab Bar、窄标题栏与项目面包屑

[变更性质] 新增移动端导航形态，前端重设计第二轮之二。
[新增功能] ≤767px 呈现底部 Tab Bar（projects/datasets/runs/account 徽标+标签+aria-current）与窄标题栏（品牌/面包屑/账户），≥768px 原桌面布局不变；ProjectPage 顶部新增"我的项目/项目名/功能页"面包屑。
[实现方案] matchMedia('(max-width: 767px)') 反应式驱动的 （Safari <14 兼容addListener 回退），tests 以 matchMedia stub 驱动真实渲染断言；保留 900px 既有断点结构以兼容 mobileCss.test.ts 正则。
[影响范围] Layout.svelte、ProjectPage.svelte；新增 mobileTabbar.test.ts。

1 files changed, 48 insertions, 0 deletions

diff --git a/frontend/src/pages/ProjectPage.svelte b/frontend/src/pages/ProjectPage.svelte
index b31caa3..fe9be7f 100644
--- a/frontend/src/pages/ProjectPage.svelte
+++ b/frontend/src/pages/ProjectPage.svelte
@@ -1,5 +1,6 @@
 <script lang="ts">
   import type { Route } from '../lib/router';
+  import { projectsStore, projectOf, projectInvisible } from '../lib/listsStore.svelte';
   import ProjectDataTab from '../pages/ProjectDataTab.svelte';
   import ProjectStrategyTab from '../pages/ProjectStrategyTab.svelte';
   import ProjectBacktestTab from '../pages/ProjectBacktestTab.svelte';
@@ -9,8 +10,28 @@
     route: Route;
   }
   let { route }: Props = $props();
+
+  // 极简面包屑：我的项目 / 项目名 / 当前标签
+  const isProject = $derived(route.name.startsWith('project-'));
+  const projectName = $derived(
+    projectOf(route.params.id)?.name ?? (projectInvisible(route.params.id) ? '不可见项目' : '加载中…')
+  );
+  const tabLabel = $derived(
+    (({ data: '数据', strategy: '策略', backtest: '回测', results: '结果' })[route.name.replace('project-', '')] ?? '')
+  );
+  $effect(() => {
+    if (isProject) void projectsStore.ensure(route.params.id).catch(() => undefined);
+  });
 </script>
 
+<nav class="crumbs" aria-label="面包屑">
+  <a href="#/projects">我的项目</a>
+  <span aria-hidden="true">/</span>
+  <span class="crumb-name">{projectName}</span>
+  <span aria-hidden="true">/</span>
+  <span class="crumb-tab">{tabLabel}</span>
+</nav>
+
 <!-- Layout is provided once by App.svelte; wrapping here produced the doubled sidebar bug. -->
 {#if route.name === 'project-data'}
   <ProjectDataTab projectId={route.params.id} />
@@ -21,3 +42,30 @@
 {:else if route.name === 'project-results'}
   <ProjectResultsTab projectId={route.params.id} runId={route.query.get('run') ?? undefined} />
 {/if}
+
+<style>
+  /* 极简面包屑（桌面 + 移动端顶部共用） */
+  .crumbs {
+    display: flex;
+    align-items: center;
+    gap: 0.45rem;
+    padding: 0.35rem 0 0.7rem;
+    font-size: 0.82rem;
+    color: var(--text-3);
+    min-width: 0;
+  }
+  .crumbs a {
+    color: var(--text-3);
+    transition: color 150ms ease;
+  }
+  .crumbs a:hover { color: var(--primary); text-decoration: none; }
+  .crumb-name {
+    color: var(--foreground);
+    font-weight: 600;
+    overflow: hidden;
+    text-overflow: ellipsis;
+    white-space: nowrap;
+    max-width: 45vw;
+  }
+  .crumb-tab { color: var(--text-2); }
+</style>