MIAMI — A key suspect in the murder investigation of Haitian President Jovenel Moïse was arrested Wednesday by federal agents in Miami after being extradited to the United States. Rodolphe Jaar, a Haitian businessman who had been convicted of U.S. cocaine-trafficking charges a decade ago, was detained by Dominican authorities earlier this month after crossing into the country following months of hiding in neighboring Haiti. The arrest of Jaar, known as “Dodof,” in the Dominican Republic came six months to the day after a hit squad allegedly made up of Colombian commandos, Haitian police office...