Implement NAPI connect() function — single SSH channel as duplex stream

- Add WraithConnectOptions struct with napi fields: server, peer, transport,
  identity (string path or Buffer), tlsServerName, insecure, irohRelay, proxy
- Add WraithStream napi class wrapping SSH channel read/write halves via
  ChannelStream::into_stream() + tokio::io::split()
- Implement connect() async function: transport creation (tcp, tls), SSH client
  connection, authenticate, open direct_tcpip channel, return WraithStream
- Identity field accepts file path (string) or in-memory key data (Buffer)
- All Rust errors marshalled to JavaScript exceptions with descriptive messages
- Add ForwardError enum to wraith-core (required by forward.rs)
- Enable tls, iroh features on wraith-core dependency
- 7 unit tests for key source resolution and address parsing

crates/wraith-napi/src/lib.rs

@@ -1,3 +1,5 @@
 #[allow(unused_imports)]
 #[macro_use]
-extern crate napi_derive;
+extern crate napi_derive;
+
+mod connect;