test(browse): smoke test for empty state and mock-fs row render

Browse was the only one of the eight HTML tools with no Playwright
spec. Added two tests at the depth of mdedit.spec.js:

  - loads with the empty state visible and add-directory button enabled
  - renders rows from a mock directory after picking

Both use the existing tests/fixtures/mock-fs-api.js machinery (no new
test scaffolding) and run in ~2s under the existing chromium-only
project.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

playwright.config.js

@@ -51,6 +51,10 @@ export default defineConfig({
       name: 'mdedit',
       testMatch: 'mdedit.spec.js',
     },
+    {
+      name: 'browse',
+      testMatch: 'browse.spec.js',
+    },
     {
       name: 'zddc',
       testMatch: 'zddc.spec.js',

tests/browse.spec.js

@@ -0,0 +1,50 @@
+import { test, expect } from '@playwright/test';
+import { MOCK_FS_INIT_SCRIPT } from './fixtures/mock-fs-api.js';
+import * as path from 'path';
+
+const HTML_PATH = path.resolve('browse/dist/browse.html');
+
+test.describe('Browse', () => {
+    test.beforeEach(async ({ page }) => {
+        await page.addInitScript(MOCK_FS_INIT_SCRIPT);
+    });
+
+    test('loads with the empty state visible and add-directory button enabled', async ({ page }) => {
+        await page.goto(`file://${HTML_PATH}`, { waitUntil: 'load' });
+        await page.waitForSelector('#addDirectoryBtn', { timeout: 15000 });
+
+        // file:// + no auto-server-root → the empty state is shown and the
+        // browse table stays hidden until the user picks a directory.
+        await expect(page.locator('#emptyState')).toBeVisible();
+        await expect(page.locator('#browseRoot')).toBeHidden();
+
+        const addDirBtn = page.locator('#addDirectoryBtn');
+        await expect(addDirBtn).toBeVisible();
+        await expect(addDirBtn).not.toBeDisabled();
+    });
+
+    test('renders rows from a mock directory after picking', async ({ page }) => {
+        await page.goto(`file://${HTML_PATH}`, { waitUntil: 'load' });
+        await page.waitForSelector('#addDirectoryBtn', { timeout: 15000 });
+
+        await page.evaluate(() => {
+            window.__setMockDirectory('docs', [
+                { name: 'spec.pdf',    content: '%PDF-fixture',           size: 1024 },
+                { name: 'readme.md',   content: '# Hello\n',              size: 8 },
+                { name: 'notes.txt',   content: 'note one\nnote two\n',   size: 16 },
+            ]);
+        });
+
+        await page.locator('#addDirectoryBtn').click();
+
+        // Browse swaps from empty state to the populated table.
+        await page.waitForSelector('#browseRoot:not(.hidden)', { timeout: 10000 });
+        await page.waitForFunction(
+            () => document.querySelectorAll('#browseTable tbody tr.tree-row').length >= 3,
+            { timeout: 10000 }
+        );
+
+        const rows = await page.locator('#browseTable tbody tr.tree-row').count();
+        expect(rows).toBeGreaterThanOrEqual(3);
+    });
+});