Nothing here is an app. This is the protocol implemented a third time, and
it is deliberately first: a third implementation is only worth writing if it
is written against the specification and the published vectors rather than
against a reading of the Swift and JavaScript that already agree.
So far: canonical bytes, safety numbers, and the RFC 6962 key log with its
inclusion and consistency proofs. Nine tests, all against the vectors the
other two engines are held to. X25519, Ed25519, X3DH, the Double Ratchet,
sealed sender and the post-quantum halves are not written yet.
The vectors are read from the protocol repository rather than copied here,
and the suite fails rather than skips when it cannot find them -- an engine
that quietly stops checking itself is worth less than no third engine.
