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>

src/features/characters/sheet/LevelUpAdvisor.tsx

@@ -0,0 +1,89 @@
+import { useState } from 'react';
+import type { Campaign, Character } from '@/lib/schemas';
+import { Button } from '@/components/ui/Button';
+import { Input } from '@/components/ui/Input';
+import { useLevelUpAdvisor } from '@/features/assistant/useLevelUpAdvisor';
+
+/**
+ * Build-route advisor shown alongside the HP-only level-up flow. Presents ~4
+ * system-aware routes (plus a custom one); choosing one expands it into concrete
+ * steps. AI-powered when configured, deterministic otherwise.
+ */
+export function LevelUpAdvisor({ campaign, character }: { campaign: Campaign; character: Character }) {
+  const { state, routes, steps, chosen, source, message, canUseLlm, fetchRoutes, chooseRoute } =
+    useLevelUpAdvisor(campaign, character);
+  const [custom, setCustom] = useState('');
+
+  if (state === 'idle') {
+    return (
+      <div className="rounded-md border border-line bg-surface p-3">
+        <div className="mb-2 text-sm text-muted">Not sure where to take this character?</div>
+        <Button size="sm" variant="secondary" onClick={fetchRoutes}>
+          {canUseLlm ? 'Suggest build routes (AI)' : 'Suggest build routes'}
+        </Button>
+      </div>
+    );
+  }
+
+  return (
+    <div className="rounded-md border border-line bg-surface p-3" data-testid="levelup-advisor">
+      <div className="mb-2 flex items-center justify-between">
+        <span className="text-xs font-semibold uppercase tracking-wide text-muted">
+          {source === 'llm' ? 'AI build routes' : 'Build routes'}
+        </span>
+        {state === 'loading' && <span className="text-xs text-muted">Thinking…</span>}
+      </div>
+      {message && <p className="mb-2 text-xs text-muted">{message}</p>}
+
+      {routes && (
+        <ul className="space-y-2">
+          {routes.map((r) => (
+            <li key={r.title} className="rounded-md border border-line p-2">
+              <div className="flex items-center justify-between gap-2">
+                <div className="min-w-0">
+                  <div className="text-sm font-medium text-ink">{r.title}</div>
+                  <div className="text-xs text-muted">{r.summary}</div>
+                  <div className="text-xs italic text-muted">{r.playstyle}</div>
+                </div>
+                <Button size="sm" variant={chosen === r.title ? 'primary' : 'secondary'} onClick={() => chooseRoute(r.title)}>
+                  Choose
+                </Button>
+              </div>
+              {chosen === r.title && steps && (
+                <ol className="mt-2 space-y-1 border-t border-line pt-2">
+                  {steps.map((s, i) => (
+                    <li key={i} className="text-sm text-ink">
+                      <span className="font-medium">{s.label}:</span> <span className="text-muted">{s.detail}</span>
+                    </li>
+                  ))}
+                </ol>
+              )}
+            </li>
+          ))}
+        </ul>
+      )}
+
+      <div className="mt-3 flex gap-2">
+        <Input
+          value={custom}
+          onChange={(e) => setCustom(e.target.value)}
+          placeholder="Or describe your own route…"
+          aria-label="Custom build route"
+          className="text-sm"
+        />
+        <Button size="sm" variant="secondary" disabled={!custom.trim()} onClick={() => chooseRoute(custom.trim())}>
+          Plan it
+        </Button>
+      </div>
+      {chosen && !routes?.some((r) => r.title === chosen) && steps && (
+        <ol className="mt-2 space-y-1 rounded-md border border-line p-2" data-testid="custom-steps">
+          {steps.map((s, i) => (
+            <li key={i} className="text-sm text-ink">
+              <span className="font-medium">{s.label}:</span> <span className="text-muted">{s.detail}</span>
+            </li>
+          ))}
+        </ol>
+      )}
+    </div>
+  );
+}