Somehow, I ended up with an NPR on the same world I had just created an empire on... not sure how that happened. Anyway, I went into the database, opened the Race table, and unchecked the "NPR" column checkbox.
Voila, it's now a player race... meaning that you can look at it in the "Race Details" screen... which has a "delete" function. Yay, all done.
Now, do beware that I don't know what that will do in a game that's well-along. I did it before I started, before I had gone 5 seconds into the game.
Also, 16? Ouch. I tried 10 with this game, it's taking a while, and I'm only in my 15th year....