Tracy Madden continues to delight as she nears the end of her first month as successor to Pat Persaud. Not only does she class up the joint, Madden also seems determined to shake off the lethargic pall that has settled over the rest of the 5, 6, and 10 p.m. broadcasts.She has, for example, proven herself capable of the quick comeback, no matter how inane the remarks from deskmates John Knicely