By Michael O’Sullivan, The Washington Post At nearly 2½ hours long, “A Cure for Wellness” may qualify as the world’s longest, most agonizing teaser. For most of that duration, the gorgeously disturbing new film by Gore Verbinski adamantly refuses to spill its secrets, which continue to mount up behind a dam of mystery so maddeningly impenetrable that it’s a wonder people don’t walk out before the climax.