“It worked.” Those are the quiet words spoken in “Oppenheimer” after the Los Alamos trial of the atomic bomb, the whispery quality of the remark in dramatic contrast to one of the most momentous events of the 20th century. The entire movie turns on similar nuances. J. Robert Oppenheimer (Cillian Murphy) is called a hero because the invention he spearheaded ended World War II. But he’s also…