CHLOE'S CLOTHES: As if four shows per time slot weren't enough to make everyone in fashion groan, Chloë Sevigny just made the schedule a little bit tighter. A latecomer to the schedule, she will present a collection for Opening Ceremony during fashion week. Sevigny is working with Opening Ceremony owner Humberto Leon and "some friends," according to an e-mail teaser from her camp. Hoping to keep things on more egalitarian ground, Sevigny has opted to show in the very civilized manner of a presentation, between noon and 6 p.m. on Sept. 10.