feat(TopBar): 添加搜索框快捷键提示功能及相关测试

- 新增 getSearchShortcutLabel 函数，根据平台返回搜索框的快捷键提示文案。
- 更新 SearchInput 组件，使用 getSearchShortcutLabel 显示正确的快捷键。
- 新增 constants.test.ts 测试文件，验证 getSearchShortcutLabel 函数在不同操作系统下的行为。
- 新增 features.lazy.test.ts 文件，测试懒加载功能，确保页面模块按需加载。

src/layout/TopBar/__tests__/constants.test.ts

@@ -0,0 +1,37 @@
+import { afterEach, describe, expect, it, vi } from 'vitest';
+import { getSearchShortcutLabel } from '@/layout/TopBar/constants';
+
+describe('getSearchShortcutLabel', () => {
+  const originalUserAgent = navigator.userAgent;
+
+  afterEach(() => {
+    vi.stubGlobal('navigator', { ...navigator, userAgent: originalUserAgent });
+  });
+
+  it('macOS 应显示 ⌘K', () => {
+    vi.stubGlobal('navigator', {
+      ...navigator,
+      userAgent:
+        'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36',
+    });
+    expect(getSearchShortcutLabel()).toBe('⌘K');
+  });
+
+  it('Windows 应显示 Ctrl+K', () => {
+    vi.stubGlobal('navigator', {
+      ...navigator,
+      userAgent:
+        'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36',
+    });
+    expect(getSearchShortcutLabel()).toBe('Ctrl+K');
+  });
+
+  it('Linux 应显示 Ctrl+K', () => {
+    vi.stubGlobal('navigator', {
+      ...navigator,
+      userAgent:
+        'Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/120.0.0.0 Safari/537.36',
+    });
+    expect(getSearchShortcutLabel()).toBe('Ctrl+K');
+  });
+});