BOSTON (AP) — The Boston Symphony Orchestra says it agreed with its musicians to a 48-hour extension of their collective bargaining agreement, allowing more time for negotiations to head off what could be the first strike in the ensemble’s 145-year history. The Boston Musicians’ Association said Saturday it had authorized a strike ahead of the expiration of the union’s three-year contract at 11:59 p. m. Sunday. The BSO said Sunday the contract had been extended to 11:59 p. m. Tuesday...