As promised last time, I’m giving you the first episode of the amateur detective drama “The Casebook of Gregory Hood,” a summer replacement series that became a hit in its own right. Written by science fiction and mystery writer Anthony Boucher and writer Denis Green, it takes full advantage of its post-war San Francisco setting. Then on the “Jack Benny Program,” Jack has to sneak around in order to avoid being seen by actor Ronald Colman. Luckily, he has his old-lady costume from a production of “Charley’s Aunt.” So on go the bonnet and high heels . .