After years of being outgunned by Japanese rivals, the American auto industry has made small cars a central part of its strategy, seeking to capitalize on a fundamental shift in the preferences of consumers in an era of fast-rising gas prices. By refocusing on small cars and de-emphasizing the gas-guzzlers that had long sustained the industry, General Motors and Ford in particular are preserving jobs and positioning themselves to prosper. Their efforts are already paying off in the marketplace. Ford