WASHINGTON — President Biden and his extended family arrived late Friday for a weeklong Lake Tahoe vacation at the $18 million waterfront mansion of billionaire climate investor Tom Steyer. Biden, 80, and his scandal-plagued son Hunter, 53, showed up separately to the six-bedroom Nevada retreat, which is touted on Redfin as “one of Lake Tahoe’s finest lakefront properties and the pinnacle waterfront estate within the gated Glenbrook community.”