init: add source code from src.zip

src/costHook.ts

@@ -0,0 +1,22 @@
+import { useEffect } from 'react'
+import { formatTotalCost, saveCurrentSessionCosts } from './cost-tracker.js'
+import { hasConsoleBillingAccess } from './utils/billing.js'
+import type { FpsMetrics } from './utils/fpsTracker.js'
+
+export function useCostSummary(
+  getFpsMetrics?: () => FpsMetrics | undefined,
+): void {
+  useEffect(() => {
+    const f = () => {
+      if (hasConsoleBillingAccess()) {
+        process.stdout.write('\n' + formatTotalCost() + '\n')
+      }
+
+      saveCurrentSessionCosts(getFpsMetrics?.())
+    }
+    process.on('exit', f)
+    return () => {
+      process.off('exit', f)
+    }
+  }, [])
+}