Wrap a random 32-byte message key with Argon2id+ChaCha20-Poly1305.
sqlite messages.plaintext is nonce||ciphertext; identity keys stay
plaintext. Empty/wrong passphrase fails closed. Ctrl-Q types CLEAR or
QUIT then Enter (Esc cancels).
prf frames are ed25519-signed, friend-visible only (unknown pubkey is ignored).
/profile edits self; F5 and /who show the selected friend's last profile.
