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/tests/transport_tests.rs

@@ -0,0 +1,26 @@
+use alknet_core::testutil::{MockTransport, MockTransportAcceptor, Transport, TransportAcceptor, mock_pair};
+
+#[tokio::test]
+async fn mock_transport_connect() {
+    let transport = MockTransport::new(1024);
+    let stream = transport.connect().await.unwrap();
+    drop(stream);
+}
+
+#[tokio::test]
+async fn mock_transport_acceptor_accept() {
+    let acceptor = MockTransportAcceptor::new(1024);
+    let (stream, info) = acceptor.accept().await.unwrap();
+    drop(stream);
+    drop(info);
+}
+
+#[tokio::test]
+async fn mock_pair_communicates() {
+    let (mut client, mut server) = mock_pair(1024);
+    use tokio::io::{AsyncReadExt, AsyncWriteExt};
+    client.write_all(b"hello").await.unwrap();
+    let mut buf = [0u8; 5];
+    server.read_exact(&mut buf).await.unwrap();
+    assert_eq!(&buf, b"hello");
+}