Phase 15: level-up strategy advisor + campaign insights

- Level-up build-route advisor (src/features/characters/sheet/LevelUpAdvisor.tsx +
  useLevelUpAdvisor): ~4 system-aware routes plus a custom one; choosing a route
  expands it into concrete next-level steps. AI when configured, deterministic
  fallback (src/lib/assistant/levelup.ts) otherwise. Embedded in the existing
  HP-only LevelUpModal, which stays primary.
- Level-up prompts/schemas added to prompts.ts (buildRoutes/buildSteps), each
  leading with the system constraint + class + next level.
- Campaign Insights section on the Assistant page renders deterministic themes,
  with an optional 'ask the assistant to expand' affordance when AI is on.

levelup + prompt unit tests (4 routes both systems, system vocabulary, custom
route); e2e for the deterministic route→steps flow and the insights section.

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

e2e/assistant-levelup.spec.ts

@@ -0,0 +1,40 @@
+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('level-up advisor offers routes and expands a chosen one (deterministic)', async ({ page }) => {
+  await page.getByLabel('Settings').click();
+  await page.getByRole('button', { name: 'Load sample campaign' }).click();
+  await expect(page.getByRole('heading', { name: 'Sample: Lost Mine' })).toBeVisible();
+
+  // Open Lia (level 3 Fighter) and start a level-up.
+  await page.getByLabel('Primary').getByRole('link', { name: 'Characters' }).click();
+  await page.getByRole('link', { name: /Lia the Brave/ }).click();
+  await page.getByRole('button', { name: 'Level up' }).click();
+
+  const advisor = page.getByTestId('levelup-advisor');
+  await page.getByRole('button', { name: 'Suggest build routes' }).click();
+  await expect(advisor).toBeVisible();
+
+  // Four system-aware routes; choose one and see concrete steps for the next level.
+  await expect(advisor.getByText('Offense')).toBeVisible();
+  await expect(advisor.getByRole('button', { name: 'Choose' })).toHaveCount(4);
+  await advisor.locator('li').filter({ hasText: 'Offense' }).getByRole('button', { name: 'Choose' }).click();
+  await expect(advisor.getByText('Level 4 focus')).toBeVisible();
+});
+
+test('assistant page renders the campaign insights section', async ({ page }) => {
+  await page.getByLabel('Settings').click();
+  await page.getByRole('button', { name: 'Load sample campaign' }).click();
+  await page.getByRole('link', { name: 'Assistant' }).click();
+  await expect(page.getByRole('heading', { name: 'Campaign insights' })).toBeVisible();
+  // Sample has a single encounter → not enough for a trend yet.
+  await expect(page.getByText(/No trends detected yet/)).toBeVisible();
+});