refactor!: rebrand wraith to alknet

Rename all crates, CLI commands, constants, type names, doc comments,
and documentation from wraith to alknet. Includes wire-protocol changes:
ALPN wraith-ssh -> alknet-ssh, reserved destination prefix wraith- ->
alknet-, SSH auth username wraith -> alknet.

crates/alknet-core/src/auth/mod.rs

@@ -0,0 +1,12 @@
+//! SSH authentication (Ed25519 public key and OpenSSH certificate authority).
+//!
+//! Supports file-path and in-memory key sources. No password authentication.
+//! See ADR-012 for the design rationale.
+
+pub mod client_auth;
+pub mod keys;
+pub mod server_auth;
+
+pub use client_auth::{ClientAuthConfig, ClientHandler};
+pub use keys::{CertAuthorityEntry, KeySource, load_private_key, load_public_keys};
+pub use server_auth::ServerAuthConfig;