feat: virtualize file tree rendering

Author: yeahhe365

structure-insight/components/FileTree.test.tsx

@@ -0,0 +1,50 @@
+import React from 'react';
+import { render, screen } from '@testing-library/react';
+import { describe, expect, it, vi } from 'vitest';
+import FileTree from './FileTree';
+import type { FileNode } from '../types';
+
+vi.mock('react-virtuoso', () => ({
+  Virtuoso: ({ data, itemContent }: any) => (
+    <div data-testid="virtuoso" data-count={String(data.length)}>
+      {data.slice(0, 12).map((item: any, index: number) => (
+        <div key={item.path}>{itemContent(index, item)}</div>
+      ))}
+    </div>
+  ),
+}));
+
+const makeLargeTree = (): FileNode[] => [
+  {
+    name: 'src',
+    path: 'src',
+    isDirectory: true,
+    children: Array.from({ length: 200 }, (_, index) => ({
+      name: `file-${index}.ts`,
+      path: `src/file-${index}.ts`,
+      isDirectory: false,
+      children: [],
+      status: 'processed' as const,
+    })),
+  },
+];
+
+describe('FileTree virtualization', () => {
+  it('passes the flattened visible rows into the virtual list instead of mounting the full tree', () => {
+    render(
+      <FileTree
+        nodes={makeLargeTree()}
+        onFileSelect={vi.fn()}
+        onDeleteFile={vi.fn()}
+        onCopyPath={vi.fn()}
+        onToggleExclude={vi.fn()}
+        selectedFilePath={null}
+        showCharCount={false}
+      />
+    );
+
+    expect(screen.getByTestId('virtuoso').getAttribute('data-count')).toBe('201');
+    expect(screen.getByText('file-0.ts')).not.toBeNull();
+    expect(screen.queryByText('file-199.ts')).toBeNull();
+  });
+});