You get the sense that Julie de Libran — former design director of Marc Jacobs’ Louis Vuitton and, before that, a designer at Prada — has been saving her best ideas for her moment in the sun, at least judging from her triumphant debut at Sonia Rykiel. Infusing two house trademarks — stripes and knits — with a bohemian spirit, she produced delectable shaggy knits, all-over fringe skirts, simplified army fatigues, and sexy diaphanous gypsy dresses worn by the boho likes of Georgia May and Lizzie Jagger. She brought it all together with a subtle splash of orange — Rykiel orange.