Space shuttle Endeavour and its seven astronauts returned to Earth on Friday, completing a long but successful construction job that boosted the size and power of the international space station. They ended up swamped with sushi. Endeavour's smooth and punctual arrival, after more than two weeks in orbit, set off a steady stream of congratulations and an ecstatic welcoming reception for Koichi Wakata, the first Japanese astronaut to return from a long space journey. His station mission lasted 4 1/2 months. At his request, sushi awaited him. But it was more than Wakata had anticipated. He was overloaded with sushi as Kennedy Space Center workers dropped off the delicacy at crew quarters. Looking remarkably fit for someone still getting used to gravity, Wakata said four hours after touchdown that he had yet to eat any sushi because of all the medical testing. But he was going to splurge as soon as the crew news conference ended.