perf(app): performance improvements

packages/app/src/components/session-context-usage.tsx

@@ -26,13 +26,17 @@ export function SessionContextUsage(props: SessionContextUsageProps) {
   const view = createMemo(() => layout.view(sessionKey))
   const messages = createMemo(() => (params.id ? (sync.data.message[params.id] ?? []) : []))
 
+  const usd = createMemo(
+    () =>
+      new Intl.NumberFormat(language.locale(), {
+        style: "currency",
+        currency: "USD",
+      }),
+  )
+
   const cost = createMemo(() => {
-    const locale = language.locale()
     const total = messages().reduce((sum, x) => sum + (x.role === "assistant" ? x.cost : 0), 0)
-    return new Intl.NumberFormat(locale, {
-      style: "currency",
-      currency: "USD",
-    }).format(total)
+    return usd().format(total)
   })
 
   const context = createMemo(() => {