By DAMIAN GARDE @damiangarde Zayyan Agboatwalla, right, at home with his mother and cousin. Agboatwalla was born with achondroplasia, the most common cause of dwarfism.LAURA MORTON FOR STAT Atreatment for the most common cause of dwarfism met its goal of increasing height in a pivotal study, the drug’s maker said Monday, setting the stage for Food and...