I guess what came to mind for me was the FFXII demo that was included with DQVIII. That's a separate entry because it's easy separated from DQVIII. But Chrono Trigger has FFCC on the disc, so it seems a little strange to separate it out of it's original entry.
I don't know if that makes sense though.
Personally, I'd say keep it the way it is because there is a chance someone could only have the demo
Keep the Chrono Trigger the way it is or the FFXII demo entry?
I would keep it as Final Fantasy Chronicles: Chrono Trigger and for the artwork, use the disc artwork since the game itself has no artwork of its own, so the Final Fantasy Chronicles: Chrono Trigger's artwork would be this:
*I submitted that as an edit, so we'll see what happens
I would keep the FFXII demo exactly as it is personally. It makes note that it was included with Dragon Quest VIII and it uses the disc (the only artwork available) as the artwork.
This same thing happened a while ago, for the NA version of Bayonetta on Wii U, there is no cover art, it was bundled only with Bayonetta 2. I tried to change it a few times to the disc artwork because it had unofficial artwork. Finally I pm'ed and admin and they accepted the disc artwork as the game's artwork because that is the official (and only) artwork for the game.