From summit to plummetOnce global leaders, Japanese electronics firms are tumbling IN TOKYO'S posh Ginza shopping district the Apple Store is packed, but the nearby Sony showroom is as lifeless as a mausoleum. In recent days the largest Japanese gadget-makers said they expect to lose a combined $17 billion in the financial year 2011. Panasonic alone expects to lose $10 billion. Meanwhile South Kor