The fourth season of Top Chef promises to be the same as the previous ones — which is to say, preposterously entertaining. The rivals are made up of the usual assortment of smug favorites, sympathetically vulnerable underdogs, foxy lady chefs, and the inevitable molecular gastronomist. This year’s crop also includes a lesbian couple — and as always, slow-speaking host Padma Lakshmi and her sidekick, Tom Colicchio. Subtle as ever, the show — set this time around in Chicago — kicks off with a deep-dish-pizza contest.