test(desktop): Playwright electron e2e harness

Launches the built app (out/main/index.js) via Playwright's _electron
API — no browser project, no chromium download. Adds a launch fixture
(electronApp/window/app), an AppPage page object with a screenshot
helper for autonomous visual review, and a boot smoke suite (shell
renders, @commitea/core label-parse runs in the renderer, preload API
exposed). Scripts: e2e (build+run), e2e:only, e2e:report. Artifacts
gitignored.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/desktop/e2e/fixtures.ts

@@ -0,0 +1,48 @@
+import { dirname, join } from 'node:path'
+import { fileURLToPath } from 'node:url'
+
+import {
+  _electron as electron,
+  expect,
+  test as base,
+  type ElectronApplication,
+  type Page,
+} from '@playwright/test'
+
+import { AppPage } from './pages/app.page.js'
+
+const here = dirname(fileURLToPath(import.meta.url))
+/** The built main-process entry Playwright launches. `yarn e2e` builds it first. */
+const MAIN_ENTRY = join(here, '..', 'out', 'main', 'index.js')
+
+interface CommiteaFixtures {
+  /** The launched Electron application. */
+  electronApp: ElectronApplication
+  /** The app's first (and only) BrowserWindow, as a Playwright Page. */
+  window: Page
+  /** Page Object over the app shell. */
+  app: AppPage
+}
+
+export const test = base.extend<CommiteaFixtures>({
+  electronApp: async ({}, use) => {
+    const electronApp = await electron.launch({
+      args: [MAIN_ENTRY],
+      env: { ...process.env, NODE_ENV: 'test', COMMITEA_E2E: '1' },
+    })
+    await use(electronApp)
+    await electronApp.close()
+  },
+
+  window: async ({ electronApp }, use) => {
+    const window = await electronApp.firstWindow()
+    await window.waitForLoadState('domcontentloaded')
+    await use(window)
+  },
+
+  app: async ({ window }, use) => {
+    await use(new AppPage(window))
+  },
+})
+
+export { expect }