docs: add comprehensive project wiki for v1.0

Co-authored-by: factory-droid[bot] <138933559+factory-droid[bot]@users.noreply.github.com>

droid-wiki/systems/socks5-proxy.md

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+# SOCKS5 proxy
+
+The SOCKS5 module in `src/socks5.rs` implements RFC 1928 (SOCKS5 protocol) and RFC 1929 (username/password authentication).
+
+## Purpose
+
+Handle the SOCKS5 handshake on the connector side, parse CONNECT requests, and resolve target addresses so that local applications can forward traffic through the tunnel.
+
+## Supported features
+
+- CONNECT command only (no BIND or UDP)
+- No-auth and username/password authentication methods
+- IPv4 and domain name targets (no IPv6)
+- Target DNS resolution on the connector side
+
+## Key abstractions
+
+| Type | File | Description |
+| ---- | ---- | ----------- |
+| `Socks5Target` | `src/socks5.rs` | Enum: `Ipv4(addr, port)` or `Domain { domain, port }` |
+| `Socks5State` | `src/socks5.rs` | State machine: ExpectGreeting → ExpectAuth → ExpectRequest → RequestReceived → Established → Closed |
+| `Socks5Error` | `src/socks5.rs` | Error enum for malformed input, unsupported methods, and parse failures |
+| `parse_greeting` | `src/socks5.rs` | Parse client greeting and choose auth method |
+| `parse_auth_request` | `src/socks5.rs` | Parse username/password auth request |
+| `parse_connect_request` | `src/socks5.rs` | Parse CONNECT request and extract target |
+| `resolve_target` | `src/socks5.rs` | Async DNS resolution of a `Socks5Target` to a `SocketAddr` |
+
+## Integration
+
+The connector's `run_socks5_proxy` in `src/tunnel.rs` calls `socks5_handshake` (an async function in `src/tunnel.rs` that uses `src/socks5.rs` constants and helpers) for each incoming SOCKS5 connection. After handshake, it opens a stream via `StreamMux::open_stream` and forwards data bidirectionally.
+
+## Key source files
+
+| File | Purpose |
+| ---- | ------- |
+| `src/socks5.rs` | SOCKS5 protocol constants, parsing, target resolution |
+| `src/tunnel.rs` | Async SOCKS5 handshake and proxy integration |