Was Groundhog Day always this deep? What strikes you now isn't how simultaneously barbed and warm Bill Murray is as he lives Feb. 2 over and over, but how simultaneously bleak and hopeful this modern classic feels: Every day is cold and lonely, the film insists, yet we can still make the most of it. EXTRAS Murray is sadly (but predictably) absent; director Harold Ramis is on hand for a mini-doc and commentary, where answering many a fan's burning question he posits that Murray's weatherman repeats the same day ''for about 10 years.'' A-

