Back navigation preserves form state

If navigating back to a previous onboarding step wipes out the data the user already entered, any attempt to correct an answer on an earlier step forces the user to re-enter every subsequent field. The user-experience taxon treats form-state preservation as table stakes for multi-step wizards: state loss on back navigation converts a typo-correction into a full restart, and a meaningful fraction of users simply abandon rather than redo five minutes of typing. This is especially punishing for users on mobile or flaky connections.

Lift form state above the step components so navigating between steps preserves it. Use react-hook-form with FormProvider in src/app/(app)/onboarding/layout.tsx so every step shares one form instance, and for route-based wizards persist values to sessionStorage and rehydrate on mount.

const methods = useForm({ defaultValues: savedData });
return (
  <FormProvider {...methods}>
    {children}
  </FormProvider>
);