This is once again very limited. We only support one `curve25519-sha256`
for the key exchange and `ssh-ed25519` as the host key.
With the SSH_DEBUG macro set and connecting from my host, it now prints:
```
Client protocol string: SSH-2.0-OpenSSH_10.0p2 Ubuntu-5ubuntu5
KEXINIT message sent
KEX_ECDH_REPLY message sent
error: Draw the rest of the owl
```
The client seems happy with the key exchange, and the following message
is encrypted!
