Composing a page from several files is why includes exist, and one endnote list
at its end is what that page wants. ADR-0066 kept the old default only so
existing content would not re-render; both models have now been seen and the
human chose. `include: embed` still asks for the other thing.
One-level needed enforcing on the new path: a spliced fragment's own include
line would otherwise be parsed as a call and expanded a second time, which a
test caught. It is dropped during the splice, matching what embed already did.