GEORGETOWN, Del. — In its glory days, the yacht Sequoia was a spit-polished, floating mini-palace, on which presidents from Herbert Hoover to Jimmy Carter entertained dignitaries and diplomats, or simply sought refuge from the Oval Office and the glare of the international spotlight.In more recent years, the privately owned, 104-foot wooden vessel, which Carter had sold in 1977, has been used for entertaining and sightseeing tours of the Potomac River, offering four-hour charters for $10,000 (plus food and drink …