The leader of Tesla Inc.’s Optimus program is leaving the company, according to a person familiar with the matter, injecting uncertainty into the humanoid robot effort that Chief Executive Officer Elon Musk sees as a significant part of its future business.Milan Kovac, the head of engineering for Optimus, informed colleagues on Friday that he is departing effective immediately, said the person, who asked not to be identified discussing private information. Ashok Elluswamy, who leads Tesla’s Auto...