Air Force Capt. Scott O'Gradytraded his Bosnian diet of grass, rainwater and ants for a feast of lamb chops and crab meat salad today alongside President Clinton in the White House. Taking in the spread, O'Grady cracked: "You'll understand, Mr. President, if I don't eat the salad." Flanked by the fighter pilot's parents, grandparents, brother and sister, Clinton and the top Pentagon brass paid tribute to the pilot's courage and to the readiness of the Marines who rescued him last Thursday. "He gave us something more precious than we can ever give him: a reminder of what is very best about our country," the President said.