TestRelaySendReceive connects two relay nodes, publishes a random payload from
one and requires the other to receive it — end-to-end over the single library.
Compiled by the PR gate; run under `make test` / locally against a built
liblogosdelivery. (Replaces the former examples/kernel, removed alongside the
ffi flatten.)
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
