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/Cargo.toml

@@ -7,6 +7,8 @@ edition = "2021"
 crate-type = ["cdylib"]
 
 [dependencies]
-wraith-core = { path = "../wraith-core" }
-napi = "3"
-napi-derive = "3"
+wraith-core = { path = "../wraith-core", features = ["tls", "iroh"] }
+napi = { version = "3", features = ["async", "error_anyhow"] }
+napi-derive = "3"
+tokio = { version = "1", features = ["io-util", "sync"] }
+russh = "0.49"