Zac Efron’s bid to move from teen idol to adult movie star continues with “Charlie St. Cloud,” the story of a college-bound golden boy whose life is upended by a car accident that kills his younger brother. It’s not the kind of movie that will allow Efron to coast on his good looks; the role requires him to demonstrate momentous despair, as his character forgoes college and female interest for an imagined, “Ghost”-like relationship with his dead brother. Charlie St. Cloud” is a delicate film — not flimsy, but fragile — that holds together on the strength of Efron’s physical presence and performance. It tells a story about love and loss and the beatings that life and time inflict on poor, suffering humanity.