docs: add README, LICENSE files, and crate/module-level doc comments

Add top-level README.md with alpha status warning, quick start guide,
architecture overview, feature flags, transport modes, auth docs, and
Node.js API examples.

Add dual LICENSE-MIT and LICENSE-APACHE files.

Add comprehensive crate-level and module-level rustdoc to all three
crates (wraith-core, wraith, wraith-napi) and all public modules
(transport, client, server, auth, socks5, error). Add doc comments to
key public types (Transport, TransportAcceptor, ConnectOptions,
ClientSession, Server, ServeOptions, KeySource, ServerAuthConfig, etc).

Update Cargo.toml files with workspace-level package metadata
(version, edition, license, repository) and crate descriptions.

crates/wraith-core/src/socks5/mod.rs

@@ -1,3 +1,10 @@
+//! SOCKS5 proxy server.
+//!
+//! Listens on a local port and routes each SOCKS5 connection through an SSH
+//! `direct-tcpip` channel. Supports SOCKS5h (domain names resolved server-side)
+//! to prevent DNS leaks. Uses the `ChannelOpener` trait to abstract over the
+//! SSH channel mechanism, making it testable without a real SSH session.
+
 mod protocol;
 
 use std::net::SocketAddr;