A homeless man suspected of robbing a Brookline Star Market grocery store and commandeering a Lexus sport utility vehicle to make his escape was arrested Friday by Boston police, officials said. Steven Michael Lovering, 44, whose last known address was 17 Court St., Boston, a homeless shelter, was wanted by Brookline police on charges of unarmed robbery and carjacking. He was arrested in downtown Boston early Friday afternoon, police said. On Wednesday, police said, Lovering passed a note to a cashier at the Star Market on Beacon Street in Brookline and grabbed the register’s cash drawer when the employee refused his demand.