relayburn-cli library surface.
The CLI ships as a binary (burn) backed by src/main.rs. This
lib.rs exists so internal modules can be unit-tested with cargo test -p relayburn-cli and so future integration tests under tests/
can reach the harness substrate without re-declaring the module tree.
Today the only public surface here is [harnesses] — legacy adapter
reference code plus the shared pending-stamp adapter factory introduced
in #248-b. Runtime launcher integrations should prefer the public
relayburn-sdk / @relayburn/sdk pending-stamp APIs.
Keeping this surface as a library crate alongside the binary lets the
Wave 2 fan-out PRs add per-adapter modules and unit tests without
disturbing main.rs.