We’ve been struck by an invasion of Zoes. Of owl-eyed ingénues with perky, quirky, life-embracing formulas for living. Whose sole purpose is to brighten the lives of pasty young men who could use sunshine in both body and soul. The Zoe in question in "Ruby Sparks" is Zoe Kazan, not only the star, but the writer of the script. In a strange round of metafictional Twister, she has written a story about a writer who writes a novel