fix: Use isSuccess guard for onboarding preferences fallback

Default to false (show dialog) when the query has successfully loaded
but data is missing, instead of silently defaulting to true (hide).
Only hide during the loading state to prevent flash.

Signed-off-by: Krishna Mohan <krishanmohank974@gmail.com>

Author: krishna9358

frontend/src/components/layout/AppLayout.tsx

@@ -95,11 +95,16 @@ export function AppLayout({ children }: AppLayoutProps) {
   const openCommandPalette = useCommandPaletteStore((state) => state.open);
 
   // Onboarding tutorial state (persisted in DB via API)
-  const { data: userPreferences, isLoading: prefsLoading } = useUserPreferences();
+  const {
+    data: userPreferences,
+    isLoading: prefsLoading,
+    isSuccess: prefsLoaded,
+  } = useUserPreferences();
   const updatePreferences = useUpdateUserPreferences();
-  const hasCompletedOnboarding = prefsLoading
-    ? true
-    : (userPreferences?.hasCompletedOnboarding ?? true);
+  // While loading: hide dialog (true). After loaded: use server value, default false for new users.
+  const hasCompletedOnboarding = prefsLoaded
+    ? (userPreferences?.hasCompletedOnboarding ?? false)
+    : true;
   const onboardingStep = useOnboardingStore((state) => state.currentStep);
   const setOnboardingStep = useOnboardingStore((state) => state.setCurrentStep);
   const completeOnboarding = () => updatePreferences.mutate({ hasCompletedOnboarding: true });

frontend/src/features/workflow-builder/WorkflowBuilder.tsx

@@ -168,9 +168,11 @@ function WorkflowBuilderContent() {
   const isMobile = useIsMobile();
 
   // Builder tour state (completion persisted in DB, step tracking is session-only)
-  const { data: userPreferences } = useUserPreferences();
+  const { data: userPreferences, isSuccess: prefsLoaded } = useUserPreferences();
   const updatePreferencesForTour = useUpdateUserPreferences();
-  const hasCompletedBuilderTour = userPreferences?.hasCompletedBuilderTour ?? true;
+  const hasCompletedBuilderTour = prefsLoaded
+    ? (userPreferences?.hasCompletedBuilderTour ?? false)
+    : true;
   const builderTourStep = useOnboardingStore((s) => s.builderTourStep);
   const setBuilderTourStep = useOnboardingStore((s) => s.setBuilderTourStep);
   const completeBuilderTour = () =>