Codex round-3: alias prose matches the gate's strength only when the
target's own contract is prose-only. An export-import alias to a
function, class, or namespace target (or an unresolvable one) is now
refused — those carry signature/member contracts the alias cannot
hold; export the declaration directly instead. Const/enum/interface/
type-alias targets keep the self-documentation contract.
Tests pin the refusal for function, class, and namespace targets;
module doc and RFC updated.