perf(client): defer chat persistence dependencies

src/stores/sync/chat-payment-success-sync.tsx

@@ -0,0 +1,47 @@
+"use client";
+
+/** Payment → Chat bridge, mounted only while the chat route is active. */
+import { useEffect, useRef } from "react";
+import { shallowEqual } from "@xstate/react";
+
+import { hasPendingChatUnlock } from "@/lib/navigation/chat_unlock_session";
+import { useChatDispatch } from "@/stores/chat/chat-context";
+import { usePaymentSelector } from "@/stores/payment/payment-context";
+
+export function ChatPaymentSuccessSync() {
+  const paymentState = usePaymentSelector(
+    (state) => ({
+      currentOrderId: state.context.currentOrderId,
+      isPaid: state.matches("paid"),
+      orderStatus: state.context.orderStatus,
+    }),
+    shallowEqual,
+  );
+  const chatDispatch = useChatDispatch();
+  const lastPaidKeyRef = useRef<string | null>(null);
+
+  useEffect(() => {
+    if (!paymentState.isPaid || !paymentState.currentOrderId) return;
+
+    const paidKey = `${paymentState.currentOrderId}:${paymentState.orderStatus}`;
+    if (lastPaidKeyRef.current === paidKey) return;
+    lastPaidKeyRef.current = paidKey;
+
+    let cancelled = false;
+    void (async () => {
+      if (await hasPendingChatUnlock()) return;
+      if (!cancelled) chatDispatch({ type: "ChatPaymentSucceeded" });
+    })();
+
+    return () => {
+      cancelled = true;
+    };
+  }, [
+    chatDispatch,
+    paymentState.currentOrderId,
+    paymentState.isPaid,
+    paymentState.orderStatus,
+  ]);
+
+  return null;
+}