Phase 9: onboarding, mobile & accessibility

- First-run welcome on the Campaigns page: what-the-app-is blurb, three feature
  highlights, and one-click "Try the sample campaign" (seedSampleCampaign) plus
  "Start your first campaign".
- Map token palette starts collapsed on small screens so the map gets the width.
- (Reduced-motion is already honoured globally in styles/globals.css.)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

e2e/onboarding.spec.ts

@@ -0,0 +1,16 @@
+import { test, expect } from '@playwright/test';
+
+test.beforeEach(async ({ page }) => {
+  await page.goto('/');
+  await page.evaluate(async () => {
+    indexedDB.deleteDatabase('ttrpg-manager');
+    localStorage.clear();
+  });
+  await page.reload();
+});
+
+test('onboarding: first-run welcome loads the sample campaign', async ({ page }) => {
+  await expect(page.getByRole('heading', { name: 'Welcome to TTRPG Manager' })).toBeVisible();
+  await page.getByRole('button', { name: 'Try the sample campaign' }).click();
+  await expect(page.getByRole('heading', { name: 'Sample: Lost Mine' })).toBeVisible();
+});