Moments after Sunday’s loss to the San Francisco Giants, Willson Contreras sat in the visitors dugout at Oracle Park when it hit him. He realized this was the Chicago Cubs’ last game before Tuesday’s 5 p.m. trade deadline. If, as expected, Contreras is traded, Sunday marked his final game with the only organization he has known since he signed as a teenager from Venezuela. So Contreras lingered, staring out at the field.