Add attention inbox and AI usage observability

tests/dashboard/performance-operations.test.tsx

@@ -83,12 +83,24 @@ describe('PerformancePage', () => {
         upsell: 3,
         images: 2,
       })),
+      http.get('/api/analytics/ai-usage', ({ request }) => {
+        expect(new URL(request.url).searchParams.get('days')).toBe('30');
+        return HttpResponse.json({
+          days: 30, requests: 12, successes: 9, refusals: 2, errors: 1,
+          promptTokens: 1200, completionTokens: 300, totalTokens: 1500,
+          costUsd: 0.0123, averageLatencyMs: 420,
+          models: [{ model: 'model-a', requests: 12, successes: 9, refusals: 2, errors: 1, promptTokens: 1200, completionTokens: 300, totalTokens: 1500, costUsd: 0.0123, averageLatencyMs: 420 }],
+        });
+      }),
     );
 
     renderPage(<PerformancePage />);
 
     expect(await screen.findByRole('heading', { name: 'Performance' })).toBeInTheDocument();
     expect(screen.getByRole('heading', { name: 'Outcome funnel' })).toBeInTheDocument();
+    expect(screen.getByRole('heading', { name: 'AI cost and reliability' })).toBeInTheDocument();
+    expect(screen.getByRole('table', { name: 'AI usage by model' })).toHaveTextContent('model-a');
+    expect(screen.getByLabelText('AI usage totals')).toHaveTextContent('$0.0123');
     expect(screen.getByText('5 awaiting maturity')).toBeInTheDocument();
     const subredditTable = screen.getByRole('table', { name: 'Subreddit performance' });
     expect(within(subredditTable).getByText('n = 40')).toBeInTheDocument();