It was the split heard 'round the showbiz world — and now it's final. No, not Brad and Jen — Mickey Mouse and the Weinsteins. On Monday, Disney formally announced that Miramax cofounders Bob and Harvey Weinstein will step down in September to launch their own film company. Disney will hold onto the Miramax name and library, while the Weinsteins will retain the Dimension label, Gwyneth Paltrow and 15 of the next 20 best picture Oscars.