Television tries always to project personality. Yet few credible personalities ever emerge. One that survived in Baltimore, from one generation to the next, was Stu Kerr, now dead at 66. He was best known for comic improvisation for kids -- Bozo the Clown, Professor Kool, Commander Stukker. But Stu Kerr did it all, straight announcing, the weather, news, fund-raising. Whether the viewer saw Professor Kool or Stu Kerr, there was no mistaking him for someone else, and no forgetting. He brought a thousand chuckles, a million smiles. He endured, a friend to all; his was positive, good humor. Stu Kerr is gone when we need him most, with no successor in sight.