Claudia Eller Co-Editor-in-ChiefHollywood insiders and movie fans are still scratching their heads over Kristen Stewart being shunned by the Screen Actors Guild last week for her ballyhooed performance as Princess Diana in “Spencer.”I too am totally mystified as to why one of the best performances of the year was ignored by Stewart’s actor peers.From the moment “Spencer” premiered to great fanfare at the Venice and Telluride film festivals, Stewart was considered the hands-down favorite to win the Oscar. I can’t imagine that she won’t score an Oscar nomination on Feb.