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/pages/app.page.ts

@@ -0,0 +1,40 @@
+import { dirname, join } from 'node:path'
+import { fileURLToPath } from 'node:url'
+
+import { expect, type Locator, type Page } from '@playwright/test'
+
+const here = dirname(fileURLToPath(import.meta.url))
+/** Where `screenshot()` drops PNGs — gitignored, readable for visual review. */
+const SCREENS_DIR = join(here, '..', '.artifacts', 'screens')
+
+/**
+ * Page Object over the CommiTea app shell. As real screens land (P3), add
+ * per-screen page objects and accessor methods here; keep locators
+ * user-facing (getByRole/getByText), never CSS/DOM structure.
+ */
+export class AppPage {
+  constructor(readonly page: Page) {}
+
+  get heading(): Locator {
+    return this.page.getByRole('heading', { name: 'CommiTea' })
+  }
+
+  /** Assert the shell has rendered. */
+  async expectLoaded(): Promise<void> {
+    await expect(this.heading).toBeVisible()
+  }
+
+  /** Read the `commitea` preload API surface from the renderer. */
+  async preloadApi(): Promise<Record<string, unknown> | undefined> {
+    return this.page.evaluate(
+      () => (globalThis as unknown as { commitea?: Record<string, unknown> }).commitea,
+    )
+  }
+
+  /** Capture a full-page screenshot for visual review; returns the path. */
+  async screenshot(name: string): Promise<string> {
+    const path = join(SCREENS_DIR, `${name}.png`)
+    await this.page.screenshot({ path, fullPage: true })
+    return path
+  }
+}