Add E2E Testing (Playwright) section to README

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

README.md

@@ -95,6 +95,7 @@ in sync with the code.
 - [Configuration Overview](#configuration-overview)
 - [Usage Workflow](#usage-workflow)
 - [Design & App Generation](#design--app-generation)
+- [E2E Testing (Playwright)](#e2e-testing-playwright)
 - [Commands Reference](#commands-reference)
 - [Skills Reference](#skills-reference)
 - [Agents Reference](#agents-reference)
@@ -440,6 +441,44 @@ See [`docs/design/README.md`](docs/design/README.md) for the full structure.
 
 ---
 
+## E2E Testing (Playwright)
+
+Every verification step in this boilerplate includes end-to-end tests. The standard verification
+sequence — used by `/add-feature`, `/execute-milestones`, and `/generate-app` — is:
+
+```bash
+npm test           # unit tests
+npm run lint
+npm run typecheck
+npm run test:e2e   # Playwright E2E
+```
+
+How it works (defined in the `e2e-testing` skill):
+
+- **Setup is automatic**: on the first verification, if Playwright is missing, the agent installs
+  `@playwright/test`, creates `playwright.config.ts` (dev-server integration, trace/screenshot on
+  failure), and adds the `test:e2e` script.
+- **Tests are derived from acceptance criteria**: each feature gets `e2e/[feature].spec.ts` with
+  one test per acceptance criterion, written before verification runs.
+- **The app shell has a smoke spec**: `/generate-app` creates `e2e/app-shell.spec.ts`, which
+  checks that the shell renders and every route in `ui-blueprint.json` navigates.
+- **Blueprint-driven locators**: tests navigate by the blueprint's routes and use semantic
+  locators (`getByRole`, `getByLabel`) — no CSS/XPath tied to implementation details, no fixed waits.
+- **No green-washing**: a failing E2E test is fixed, never skipped or deleted; milestone gates in
+  `/execute-milestones` do not pass without a green E2E suite.
+
+```
+e2e/
+├── app-shell.spec.ts        # smoke: shell renders, all blueprint routes navigate
+├── [feature-name].spec.ts   # one spec per feature (acceptance criteria)
+└── helpers/                 # shared fixtures (only when duplicated 3+ times)
+```
+
+Playwright covers the `web` target; for `flutter` the equivalent is `integration_test`, and for
+`winui3` the platform's UI automation — with the same acceptance-criteria mapping.
+
+---
+
 ## Commands Reference
 
 | Command | Description | Example |