perf: parallelize E2E tests for faster execution

- Enable fullyParallel and increase workers (4 local, 2 CI)
- Split tests into 3 projects: readonly (parallel), mutations (serial), setup-wizard (serial)
- Add serial mode to describe blocks with shared state
- Fix tests expecting wrong page after admin default changed to observability

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: mchestr

e2e/accessibility.spec.ts

@@ -5,6 +5,7 @@ import { waitForAdminContent, WAIT_TIMEOUTS } from './helpers/test-utils';
 test.describe('Accessibility Tests', () => {
   test.describe('Admin Pages', () => {
     test('admin users page should have no critical accessibility violations', async ({ adminPage }) => {
+      await adminPage.locator('aside').getByTestId('admin-nav-users').first().click();
       await waitForAdminContent(adminPage, [
         { type: 'heading', value: 'Users' }
       ]);
@@ -178,6 +179,7 @@ test.describe('Accessibility Tests', () => {
 
   test.describe('Interactive Elements', () => {
     test('icon buttons should have accessible names', async ({ adminPage }) => {
+      await adminPage.locator('aside').getByTestId('admin-nav-users').first().click();
       await waitForAdminContent(adminPage, [
         { type: 'heading', value: 'Users' }
       ]);

e2e/admin-functionality.spec.ts

@@ -3,7 +3,8 @@ import { verifyPageAccessible, waitForAdminContent, waitForAdminPageReady } from
 
 test.describe('Admin Functionality', () => {
   test('should access admin dashboard', async ({ adminPage }) => {
-    // After authentication, adminPage starts on /admin/users (dashboard)
+    // Admin lands on observability page, navigate to users
+    await adminPage.locator('aside').getByTestId('admin-nav-users').first().click();
     await waitForAdminContent(adminPage, [
       { type: 'heading', value: /Users/i }
     ], { timeout: 30000 });
@@ -20,7 +21,8 @@ test.describe('Admin Functionality', () => {
   });
 
   test('should access admin users list', async ({ adminPage }) => {
-    // Already on /admin/users; verify heading first
+    // Navigate to users page
+    await adminPage.locator('aside').getByTestId('admin-nav-users').first().click();
     await waitForAdminContent(adminPage, [
       { type: 'heading', value: 'Users' }
     ], { timeout: 30000 });

e2e/admin-maintenance.spec.ts

@@ -220,6 +220,9 @@ test.describe('Admin Maintenance Feature', () => {
     });
 
     test.describe('Candidate Review Workflow', () => {
+      // These tests share seeded data and must run sequentially
+      test.describe.configure({ mode: 'serial' });
+
       test.beforeAll(async () => {
         await seedMaintenanceData(prisma);
       });
@@ -407,6 +410,9 @@ test.describe('Admin Maintenance Feature', () => {
   });
 
   test.describe('Maintenance History', () => {
+    // These tests share seeded data and must run sequentially
+    test.describe.configure({ mode: 'serial' });
+
     test.beforeAll(async () => {
       await seedMaintenanceData(prisma);
     });

e2e/onboarding-flow.spec.ts

@@ -3,6 +3,9 @@ import { createE2EPrismaClient } from './helpers/prisma';
 import { waitForLoadingGone } from './helpers/test-utils';
 
 test.describe('Onboarding Flow', () => {
+  // This test modifies user onboarding state and must run in isolation
+  test.describe.configure({ mode: 'serial' });
+
   test('new user completes onboarding and is redirected to homepage', async ({ browser }) => {
     const prisma = createE2EPrismaClient();
 

e2e/user-scenarios.spec.ts

@@ -6,6 +6,9 @@ import {
 } from './helpers/test-utils';
 
 test.describe('User Scenarios', () => {
+  // These tests modify user data (wrapped content) and must run sequentially
+  test.describe.configure({ mode: 'serial' });
+
   test.describe('Authentication & Authorization', () => {
     test('both user types can authenticate successfully', async ({ adminPage, regularUserPage }) => {
       // Admin page should be on home after auth

playwright.config.ts

@@ -9,12 +9,12 @@ console.log(`Running tests on ${baseURL}`);
  */
 export default defineConfig({
   testDir: './e2e',
-  fullyParallel: false,
+  fullyParallel: true, // Enable parallel test execution within files
   /* Fail the build on CI if you accidentally left test.only in the source code. */
   forbidOnly: !!process.env.CI,
   /* Retry on CI only */
   retries: process.env.CI ? 2 : 0,
-  workers: 1, // Run tests sequentially to avoid database race conditions
+  workers: process.env.CI ? 2 : 4, // Parallel workers (tests with shared state use serial mode)
   /* Reporter to use. See https://playwright.dev/docs/test-reporters */
   reporter: [
     ['list'], // Console output
@@ -40,16 +40,37 @@ export default defineConfig({
   /* Set up database before running tests */
   globalSetup: require.resolve('./e2e/global-setup.ts'),
 
-  /* Configure projects for major browsers */
+  /* Configure projects for different test types */
   projects: [
+    // Read-only tests can run in parallel (no shared state mutations)
     {
-      name: 'chromium',
+      name: 'readonly',
+      testMatch: [
+        /accessibility\.spec\.ts/,
+        /admin-functionality\.spec\.ts/,
+        /admin-observability\.spec\.ts/,
+        /admin-protection\.spec\.ts/,
+      ],
       use: { ...devices['Desktop Chrome'] },
-      testIgnore: /setup-wizard\.spec\.ts/,
     },
+    // Tests that mutate shared state must run sequentially
+    {
+      name: 'mutations',
+      testMatch: [
+        /admin-maintenance\.spec\.ts/,
+        /onboarding-flow\.spec\.ts/,
+        /public-flows\.spec\.ts/,
+        /user-scenarios\.spec\.ts/,
+      ],
+      fullyParallel: false,
+      workers: 1,
+      use: { ...devices['Desktop Chrome'] },
+    },
+    // Setup wizard runs in complete isolation
     {
       name: 'setup-wizard',
       testMatch: /setup-wizard\.spec\.ts/,
+      fullyParallel: false,
       workers: 1,
       use: { ...devices['Desktop Chrome'] },
     },