Cocooned in Issey Miyake’s 2018 World dress, a pleated confection of silk imprinted with aerial photography of the planet, a blue — yes, blue — mannequin floats above nearly 100 iconic fashion and home-decor designs at JF Chen’s 5,000-square-foot C Project gallery, in Los Angeles. For the aptly named “Collision” exhibition, which runs through May, …