The leader and five more of the 15 titles on a current paperback best-seller list are cartoon books about cats. To say there is not a dog in the lot is to be literally true but figuratively controversial. For not all the attitudes toward cats in these pages are as affectionate as cat people might hope. Cats themselves, of course, do not demand affection when abject deference is available. Six best sellers are at least a start toward what cats would regard as equity.