It is more about schemas and reliably merging documents as far as I can tell. But weirdly given its focus on schemas I couldn't find any way for a document to link to a schema in-band!
In cue there's no real distinction between "schemas" and "documents". If you say:
value: string
value: "abc"
For Cue you would probably just want to #include a file... but as far as I know you can't do that.
That makes it far less useful for IDEs, linters and so on.
I don't think there's any reason they couldn't add that feature. Just a bit odd that they haven't already.
Not really sure what you mean by "documents" though.