Harden server draft sync (Save & Exit + post-login transfer)

app/create/context/CreateFlowDraftSaveBannerContext.tsx

@@ -0,0 +1,51 @@
+"use client";
+
+import {
+  createContext,
+  useContext,
+  useMemo,
+  useState,
+  type ReactNode,
+} from "react";
+
+type CreateFlowDraftSaveBannerContextValue = {
+  draftSaveBannerMessage: string | null;
+  setDraftSaveBannerMessage: (_message: string | null) => void;
+};
+
+const CreateFlowDraftSaveBannerContext =
+  createContext<CreateFlowDraftSaveBannerContextValue | null>(null);
+
+export function CreateFlowDraftSaveBannerProvider({
+  children,
+}: {
+  children: ReactNode;
+}) {
+  const [draftSaveBannerMessage, setDraftSaveBannerMessage] = useState<
+    string | null
+  >(null);
+
+  const value = useMemo(
+    () => ({
+      draftSaveBannerMessage,
+      setDraftSaveBannerMessage,
+    }),
+    [draftSaveBannerMessage],
+  );
+
+  return (
+    <CreateFlowDraftSaveBannerContext.Provider value={value}>
+      {children}
+    </CreateFlowDraftSaveBannerContext.Provider>
+  );
+}
+
+export function useCreateFlowDraftSaveBanner(): CreateFlowDraftSaveBannerContextValue {
+  const ctx = useContext(CreateFlowDraftSaveBannerContext);
+  if (!ctx) {
+    throw new Error(
+      "useCreateFlowDraftSaveBanner must be used within CreateFlowDraftSaveBannerProvider",
+    );
+  }
+  return ctx;
+}