Warn on tab close when create-flow module or wizard edits have not been saved.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/hooks/useBeforeUnloadGuard.ts

@@ -0,0 +1,33 @@
+"use client";
+
+import { useEffect } from "react";
+
+/**
+ * Attach the browser’s native leave-site prompt while `enabled` is true.
+ *
+ * Modern browsers ignore custom copy; this only blocks accidental tab or
+ * window close. No-ops during SSR and when `enabled` is false so clean
+ * sessions never register a listener.
+ *
+ * @param enabled Whether unsaved work would be lost on unload.
+ *
+ * @example
+ * useBeforeUnloadGuard(isWizardSessionDirty());
+ */
+export function useBeforeUnloadGuard(enabled: boolean): void {
+  useEffect(() => {
+    if (!enabled || typeof window === "undefined") {
+      return;
+    }
+
+    const onBeforeUnload = (event: BeforeUnloadEvent) => {
+      event.preventDefault();
+      event.returnValue = "";
+    };
+
+    window.addEventListener("beforeunload", onBeforeUnload);
+    return () => {
+      window.removeEventListener("beforeunload", onBeforeUnload);
+    };
+  }, [enabled]);
+}