test: add playwright suite.

.github/workflows/playwright.yml

@@ -0,0 +1,61 @@
+name: Playwright
+
+on:
+  push:
+    branches:
+      - main
+    paths:
+      - 'src/**'
+      - 'package-lock.json'
+  pull_request:
+    branches:
+      - main
+  workflow_dispatch:
+
+jobs:
+  e2e:
+    name: E2E (Playwright)
+    runs-on: ubuntu-latest
+    timeout-minutes: 25
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v6.0.1
+
+      - name: Setup Node
+        uses: actions/setup-node@v6.2.0
+        with:
+          node-version: '24.14.0'
+
+      - name: Install Dependencies
+        run: npm ci
+
+      - name: Check Types
+        run: npm run check-types
+
+      - name: Lint Playwright Files
+        run: npm run lint:playwright
+
+      - name: Install Browsers
+        run: npx playwright install --with-deps chromium webkit
+
+      - name: Run Playwright Tests
+        env:
+          CI: 'true'
+        run: npm run test:e2e
+
+      - name: Upload Playwright report
+        uses: actions/upload-artifact@v6.0.0
+        if: ${{ failure() }}
+        with:
+          name: playwright-report
+          path: playwright-report
+          if-no-files-found: ignore
+
+      - name: Upload Playwright test results
+        uses: actions/upload-artifact@v6.0.0
+        if: ${{ failure() }}
+        with:
+          name: test-results
+          path: test-results
+          if-no-files-found: ignore

.gitignore

@@ -1,2 +1,4 @@
 node_modules
-dist
+dist
+playwright-report
+test-results

README.md

@@ -22,6 +22,22 @@ npm run dev
 
 Then open the URL printed by the dev server (it should open `src/index.html`).
 
+## End-to-end tests
+
+Run local Playwright tests (Chromium):
+
+```bash
+npm run test:e2e
+```
+
+Run locally with headed browser:
+
+```bash
+npm run test:e2e:headed
+```
+
+CI runs Playwright on Chromium and WebKit.
+
 ## Notes
 
 - This is currently a development playground, not a stable product.

eslint.config.js

@@ -0,0 +1,28 @@
+import playwright from 'eslint-plugin-playwright'
+import tsParser from '@typescript-eslint/parser'
+
+const playwrightConfig = playwright.configs['flat/recommended']
+
+export default [
+  {
+    ignores: [
+      'dist/**',
+      'coverage/**',
+      'node_modules/**',
+      'playwright-report/**',
+      'test-results/**',
+    ],
+  },
+  {
+    files: ['playwright/**/*.{ts,tsx,js,jsx}', 'playwright.config.ts'],
+    languageOptions: {
+      parser: tsParser,
+      sourceType: 'module',
+      ecmaVersion: 'latest',
+    },
+  },
+  {
+    ...playwrightConfig,
+    files: ['playwright/**/*.{ts,tsx,js,jsx}'],
+  },
+]