It’s been a hard year for the trustees of Shoreline Unified School District. Budget woes, painful staffing cuts, clashes with the superintendent, transitions and substitutes in key administrative positions, and community pressure for board members to relinquish their health benefits have challenged these seven elected officials. Given the fractious last year, the board’s annual retreat on Monday at the Tomales Regional History Center, facilitated by Linda Sheppard of the Marin County Office of Education  and…