WORCESTER — The Planning Board Wednesday approved a definitive site plan amendment for the nearly complete Polar Park that effectively memorializes small design changes, including tweaks that the board had suggested when it approved the original site plan in Nov. 2019. Discussion of some of those changes came with hints at how the newly reconfigured Summit Street will function as a sealed off extension of the park on game days at Polar Park, the city-owned ballpark that will be the home of the top minor league baseball affiliate of the Boston Red Sox starting in May. Stephen Rolle, the city's assistant chief development officer, said that included in the various design changes throughout the construction process were changes that addressed most of the board's concerns surrounding the width of sidewalks around the Canal District stadium.