Gov. Edward J. King signed legislation ending a 26-hour court-ordered shutdown of the deficit-ridden Boston-area transit system, clearing the way for service to resume for its more than 250,000 daily commuters. The shutdown had left thousands of shoppers and commuters without public transportation Saturday on what is usually one of the busiest shopping days of the Christmas season. The bill to bail out the bankrupt system, overwhelmingly passed by both legislative branches, provides for major managerial and fiscal reforms of the system, and $41 million to keep it operating until Jan. 1.