feat(gio): implement POSIX sockets proxy for WASM networking

[superstructor]

Add WebSocket-based POSIX sockets proxy client to enable TCP/HTTP connectivity in WASM builds via Cloudflare Workers backend.

Architecture

WASM (glib.wasm) <--WebSocket--> Cloudflare Workers <--TCP--> Internet
     │                                  │
     │ Binary protocol                  │
     │ (19 message types)               │
     └─ GIO APIs work unchanged         └─ Real TCP sockets

Changes

New Files:

• gio/gposixsocketsproxy.h: Proxy client API declarations

• gio/gposixsocketsproxy.c: WebSocket client with binary protocol (1335 lines)

  • Implements 19 POSIX socket operations (socket, connect, send, recv, etc.)
  • Uses Emscripten WebSocket API for communication
  • Async message queue for request/response matching
  • Thread-safe with GMutex protection

• gio/tests/gio-proxy-test.c: Integration tests (322 lines)

  • Test socket creation, DNS resolution, TCP connections
  • HTTP GET request/response validation
  • High-level GSocketClient API testing

Modified Files:

• gio/gsocket.c: Integrated proxy into GSocket operations (114 lines)

  • g_socket(): Use proxy_socket() on Emscripten
  • g_socket_connect(): Use proxy_connect() on Emscripten
  • send/recv: Use proxy_send()/proxy_recv() on Emscripten
  • Automatic proxy initialization with configurable URL

• gio/meson.build: Add proxy sources for Emscripten builds

• deno.json: Add test:proxy and test:proxy:local tasks

Protocol

Binary protocol with little-endian encoding, 19 message types matching Emscripten's POSIX sockets proxy specification:

• SOCKET, CONNECT, SEND, RECV, SHUTDOWN
• BIND, LISTEN, ACCEPT
• GETSOCKNAME, GETPEERNAME
• GETSOCKOPT, SETSOCKOPT
• GETADDRINFO, GETNAMEINFO
• SENDTO, RECVFROM, SENDMSG, RECVMSG, SOCKETPAIR

Configuration

Set proxy URL via environment variable:

export POSIX_PROXY_URL="wss://posix-proxy.discere.cloud/v1"

Defaults to wss://posix-proxy.discere.cloud/v1 if not set.

Testing

# Build WASM with proxy support
deno task build:wasm

# Test with production proxy
deno task test:proxy

# Test with local proxy (development)
deno task test:proxy:local

Benefits

• ✅ Full GIO networking API support in WASM
• ✅ GSocket, GSocketClient, GSocketConnection work unchanged
• ✅ DNS resolution via proxy_getaddrinfo()
• ✅ HTTP requests through proxy tunnel
• ✅ Zero changes required to existing GIO client code
• ✅ Thread-safe proxy operations

Impact

Enables TCP/HTTP connectivity for all GIO-based applications compiled to WASM, unlocking network-dependent features like HTTP clients, WebSocket connections, and remote API access.