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/tsconfig.json

@@ -0,0 +1,10 @@
+{
+  "extends": "../../../tsconfig.base.json",
+  "compilerOptions": {
+    "lib": ["ES2022", "DOM", "DOM.Iterable"],
+    "types": ["node"],
+    "moduleResolution": "Bundler",
+    "noEmit": true
+  },
+  "include": ["."]
+}