Only a few feet beyond the outstretched glove of Giants centerfielder Angel Pagan, over the outfield fence at AT&T Park, is a hidden gem unlike any other in big league baseball. This special space has been transformed into a lush garden with kale and Swiss chard, tomatoes and avocadoes, blueberry and lemon trees, and planter boxes packed with fresh herbs that fans are encouraged to pick and sprinkle on their food. ''There's the sustainable part of it, but there's also the health food aspect of it,'' Giants CEO Larry Baer said.