Nanushka is planting roots in Paris — at least through winter — with a six-month pop-up opening Thursday inside Galeries Lafayette, the next big step in the brand’s global growth plan. The brand already has flagships in Budapest, London and New York, and has imported Nanushka’s design DNA into an 88-square-foot physical space, a petite spot of prime real estate next to the highly trafficked Skims on the second floor of the historic department store.