Carolee Schneemann was a groundbreaking feminist performance artist. But when poor health limited her ability to create art like she used to, she turned to an unusual collaborator – her cat, La Niña. The resulting exhibit, entitled “Tooth and Paw,” opened last night in Chelsea. It features sculptures assembled by La Niña, alongside text and photos by Schneemann, who died this past March. Moira Warburton reports.