Unassuming, media-shy and, as yet, unproven, Jay Y. Lee is the unofficial heir-apparent to lead Samsung Electronics Co Ltd, as the world’s biggest technology group by sales approaches a crossroads after years of explosive growth. The only son of Samsung’s frail 72-year-old chairman Lee Kun-hee, Jay has been groomed for years to take over the sprawling South Korean family-run \”chaebol\”, a conglomerate with interests spanning technology and insurance to shipbuilding and construction.