feat: add e2e test harness (#1237)

Co-authored-by: Christian Pillsbury <cpillsbury@mux.com>

.github/workflows/e2e.yml

@@ -0,0 +1,81 @@
+name: E2E Tests
+
+on:
+  push:
+    branches:
+      - main
+      - 'release-please--branches--main'
+  pull_request:
+    types: [opened, labeled, synchronize]
+
+jobs:
+  e2e:
+    name: E2E (${{ matrix.browser }})
+    if: github.event_name == 'push' || contains(github.event.pull_request.labels.*.name, 'test:e2e')
+    runs-on: ubuntu-latest
+    container:
+      image: mcr.microsoft.com/playwright:v1.59.1-noble
+    timeout-minutes: 15
+    strategy:
+      fail-fast: false
+      matrix:
+        browser: [chromium, webkit]
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v5
+
+      - name: Setup pnpm
+        uses: pnpm/action-setup@v4
+
+      - name: Setup Node.js
+        uses: actions/setup-node@v5
+        with:
+          node-version-file: '.nvmrc'
+          cache: pnpm
+
+      - name: Install dependencies
+        run: pnpm install --frozen-lockfile
+
+      - name: Cache turbo build
+        uses: actions/cache@v5
+        with:
+          path: .turbo
+          key: ${{ runner.os }}-turbo-e2e-${{ github.sha }}
+          restore-keys: |
+            ${{ runner.os }}-turbo-e2e-
+            ${{ runner.os }}-turbo-
+
+      - name: Build packages
+        run: pnpm build:packages
+
+      - name: Build CDN bundles
+        run: pnpm build:cdn
+
+      - name: Build ejected skins
+        run: pnpm -F site ejected-skins
+
+      - name: Generate E2E test pages
+        run: pnpm --dir apps/e2e generate-pages
+
+      - name: Sync ejected skins to E2E app
+        run: pnpm --dir apps/e2e sync-ejected-skins
+
+      - name: Run E2E tests
+        run: pnpm --dir apps/e2e exec playwright test --project=vite-${{ matrix.browser }}
+
+      - name: Upload test report
+        if: always()
+        uses: actions/upload-artifact@v4
+        with:
+          name: playwright-report-${{ matrix.browser }}
+          path: apps/e2e/playwright-report/
+          retention-days: 14
+
+      - name: Upload test traces
+        if: failure()
+        uses: actions/upload-artifact@v4
+        with:
+          name: playwright-traces-${{ matrix.browser }}
+          path: apps/e2e/test-results/
+          retention-days: 7