feat: wire FileExplorer, DocumentEditor, search and upload into App

frontend/src/App.tsx

@@ -1,7 +1,46 @@
+import { useState } from 'react';
+import FileExplorer from './components/FileExplorer';
+import DocumentEditor from './components/DocumentEditor';
+import SearchBar from './components/SearchBar';
+import SearchResults from './components/SearchResults';
+import UploadButton from './components/UploadButton';
+import type { SearchResult, UploadDocumentResponse } from './api/client';
+
 export default function App() {
+  const [selectedKey, setSelectedKey] = useState<string | null>(null);
+  const [searchQuery, setSearchQuery] = useState('');
+  const [searchResults, setSearchResults] = useState<SearchResult[]>([]);
+
+  function handleJumpToResult(key: string) {
+    setSelectedKey(key);
+    setSearchQuery('');
+    setSearchResults([]);
+  }
+
+  function handleUploaded(result: UploadDocumentResponse) {
+    setSelectedKey(result.key);
+  }
+
   return (
     <div className="app">
-      <h1>DocHub</h1>
+      <div className="topbar">
+        <h1>DocHub</h1>
+        <SearchBar onQueryChange={setSearchQuery} onResults={setSearchResults} />
+        <UploadButton path="" onUploaded={handleUploaded} />
+      </div>
+      <div className="body">
+        <FileExplorer onSelectFile={setSelectedKey} selectedKey={selectedKey} />
+        <div className="main" data-testid="main-area">
+          {selectedKey ? (
+            <DocumentEditor documentKey={selectedKey} />
+          ) : (
+            <div data-testid="empty-state">未选择文档</div>
+          )}
+        </div>
+        {searchQuery !== '' && (
+          <SearchResults query={searchQuery} results={searchResults} onJumpToResult={handleJumpToResult} />
+        )}
+      </div>
     </div>
   );
 }

frontend/tests/App.test.tsx

@@ -1,8 +1,102 @@
 import { render, screen } from '@testing-library/react';
-import { test, expect } from 'vitest';
+import { test, expect, beforeEach, vi } from 'vitest';
 import App from '../src/App';
+import userEvent from '@testing-library/user-event';
+import { waitFor } from '@testing-library/react';
+import { listDocuments, getDocument, search } from '../src/api/client';
+
+vi.mock('../src/api/client');
+
+vi.mock('@monaco-editor/react', () => ({
+  default: ({ value, onChange }: { value: string; onChange: (value: string | undefined) => void }) => (
+    <textarea
+      data-testid="monaco-editor-mock"
+      value={value}
+      onChange={(e) => onChange(e.target.value)}
+    />
+  ),
+}));
+
+beforeEach(() => {
+  vi.mocked(listDocuments).mockReset();
+  vi.mocked(getDocument).mockReset();
+  vi.mocked(search).mockReset();
+  vi.mocked(listDocuments).mockResolvedValue({ folders: [], files: [] });
+  vi.mocked(getDocument).mockResolvedValue({
+    key: '',
+    content: '',
+    contentType: 'text/markdown',
+  });
+  vi.mocked(search).mockResolvedValue({ results: [] });
+});
 
 test('renders the DocHub heading', () => {
   render(<App />);
   expect(screen.getByRole('heading', { name: 'DocHub' })).toBeInTheDocument();
 });
+
+test('shows an empty state and a file tree when no document is selected', async () => {
+  vi.mocked(listDocuments).mockResolvedValue({
+    folders: [],
+    files: [{ key: '产品文档/架构设计.md', name: '架构设计.md', size: 100, modifiedAt: '2026-08-01T10:00:00Z' }],
+  });
+
+  render(<App />);
+
+  expect(screen.getByTestId('empty-state')).toBeInTheDocument();
+  expect(await screen.findByText('架构设计.md')).toBeInTheDocument();
+});
+
+test('selecting a file from the tree loads it into the editor', async () => {
+  vi.mocked(listDocuments).mockResolvedValue({
+    folders: [],
+    files: [{ key: '产品文档/架构设计.md', name: '架构设计.md', size: 100, modifiedAt: '2026-08-01T10:00:00Z' }],
+  });
+  vi.mocked(getDocument).mockResolvedValue({
+    key: '产品文档/架构设计.md',
+    content: '# 架构设计',
+    contentType: 'text/markdown',
+  });
+  const user = userEvent.setup();
+
+  render(<App />);
+
+  const fileRow = await screen.findByText('架构设计.md');
+  await user.click(fileRow);
+
+  const textarea = await screen.findByTestId('monaco-editor-mock');
+  expect(textarea).toHaveValue('# 架构设计');
+});
+
+test('searching shows the results overlay, and clicking a result opens the document', async () => {
+  vi.mocked(listDocuments).mockResolvedValue({ folders: [], files: [] });
+  vi.mocked(search).mockResolvedValue({
+    results: [{ key: '产品文档/架构设计.md', title: '架构设计.md', path: '产品文档', snippet: '...<em>检索</em>...' }],
+  });
+  vi.mocked(getDocument).mockResolvedValue({
+    key: '产品文档/架构设计.md',
+    content: '# 架构设计',
+    contentType: 'text/markdown',
+  });
+  const user = userEvent.setup();
+
+  render(<App />);
+
+  const searchInput = screen.getByRole('textbox', { name: '搜索文档' });
+  await user.type(searchInput, '检索');
+
+  await waitFor(
+    () => {
+      expect(screen.getByTestId('search-result-产品文档/架构设计.md')).toBeInTheDocument();
+    },
+    { timeout: 1000 }
+  );
+
+  await user.click(screen.getByTestId('search-result-产品文档/架构设计.md'));
+
+  await waitFor(() => {
+    expect(screen.queryByTestId('search-results')).not.toBeInTheDocument();
+  });
+  const textarea = await screen.findByTestId('monaco-editor-mock');
+  expect(textarea).toHaveValue('# 架构设计');
+});