ADR-054 prescribes with a re-export
module, but cargo rejects the cyclic dependency (alknet-tty →
alknet-tty-local → alknet-tty) even with an optional dep. The re-export
is deferred to the assembly layer: consumers depend on alknet-tty-local
directly and register LocalTtyBackend in the TtyAdapter backend map.
The feature gate stays declared (empty) for forward compatibility.
Assembly pattern documented in the crate root doc comment.