Laughter, not tears Save your tears. There was no melancholy at Isabel Marant tonight, only laughter, hugs, and champagne-fueled joy. Backstage felt like a family reunion at sunset:warm, radiant, a little chaotic. After thirty years, Isabel Marant is stepping down from designing her own label, the one that exported the very concept of the Cool French Girl  (and, frankly, the Cool French Boy) to the rest of the world. That nonchalant Parisian swagger, the tousled hair, the slo