The custom part type editor doesn't make it clear when a part type is ready for use

In particular, I always forget to fill in the description field, and that means the CPT doesn't show up in the question editor.

And maybe the question editor should show CPTs I have written but which are not yet usable, so I know what's wrong!

The issue names the custom part type editor and question editor but no files or tests. Start by reproducing a custom part type with an empty description, then trace why it is hidden from the question editor; done means the editor clearly communicates readiness and explains or exposes incomplete part types as intended.

Written by the indexing model from the issue text.