WASHINGTON — President Joe Biden is a man who writes down his thoughts. And some of those handwritten musings over his decades of public service are now a part of a special counsel’s investigation into the handling of classified documents.It isn’t clear yet what the investigators are looking for by taking custody of notes from his time as vice president and his decades in the Senate that were found in his Delaware homes in Rehoboth Beach and Wilmington.Biden’s attorneys did not say whether the notes …