The old recession playbook said consumers under financial pressure would trade down to the cheapest meal they could find. That's not what's happening these days. Instead, Americans are eating out less often, scrutinizing every restaurant purchase, and concentrating their spending among a shrinking group of perceived winners. And increasingly, those winners look a lot like Chipotle and Cava . A year ago, fast-casual chains built around customizable bowls and salads were among the restaurant