Bitter Sweet By Sarah Stegall Copyright © 2008 by Sarah Stegall Chuck Mondays on NBC at 9/8 “Chuck vs. Santa Claus” Written by Scott Rosenbaum Directed by Robert Duncan McNeill Talk about a fulcrum (turning point). The sweet, funny comedy that was Chuck turned dark and angsty in the last five minutes of this end-of-the-year episode. How very typical of this show that an episode full of elves, shiny presents, and Santa comes down to a moment of true grief for Charles Bartowski and his little friend Morgan. The ending of this episode could have permanently harshed the mellow for Chuck, but the…