Runs the form’s existing submit-preparation path (validation, BSB checks,
attachments, and the same error UI as a real submit).
Resolves with FormSubmissionAttemptAllowNavigation when the host may
continue (for example approve and upload an edit). Resolves false when
preparation failed; field errors and toasts have already been shown. Does
not call onSubmit, captcha, or analytics.
Runs the form’s existing submit-preparation path (validation, BSB checks, attachments, and the same error UI as a real submit).
Resolves with FormSubmissionAttemptAllowNavigation when the host may continue (for example approve and upload an edit). Resolves
falsewhen preparation failed; field errors and toasts have already been shown. Does not callonSubmit, captcha, or analytics.