“Past Lives,” Celine Song’s gorgeously heady and heartfelt love story, opens with its own wry version of a “three characters walk into a bar” joke. John Magaro, left, and Greta Lee in the movie “Past Lives.” By skipping over Nora’s teenage and early adult years, Song elides a lot of details and short-circuits a lot of potential immigrant-experience clichés. Crucially, …
