A member of the stage crew was doing some last-minute cleanup of the set at the Shubert, in preparation for a rehearsal of Yale Opera’s The Rake’s Progress, the opera by Igor Stravinsky set to run at the venerable College Street theatre Feb. 17 and 18. At first glance, it may have looked like he was vacuuming a vast Persian rug. A second glance, however, might show the design on the floor for what it really is: the back of an enormous playing card. More than just an arresting visual pattern, the scintillating floor is part of a set design decision that, for the opera’s director, was the key to opening up Stravinsky’s work to better connect with audiences.