Was the brownish blood the questioner saw during her Hajj a continuation of menstruation or istihadah (non-menstrual vaginal bleeding), and does that affect the validity of her Hajj and her marriage?

These brown discharges after purification from menstruation are 'kudrah' (discolored discharge). They are considered menstruation if they occur during the regular period of menstruation, but not otherwise. Purification is not a condition for any of the rituals of Hajj except for circumambulation (Tawaf). Your Hajj and your marriage are valid, and nothing is required of you, because this 'kudrah' after purification is not considered menstruation.