Implement WebSocket JS API (new WebSocket, send, close, events) #187

Goal#

Expose the WebSocket protocol implementation to JavaScript via the standard WebSocket interface, wired into the main event loop and the Web Workers runtime.

Depends on: "Implement WebSocket protocol (RFC 6455) in we-net".

Scope#

• Constructor
  • new WebSocket(url, protocols?) where protocols is a string or array of strings
  • URL must be ws: or wss:; throw SyntaxError otherwise
  • Asynchronous connect — return immediately, dispatch open or error later via the event loop
• Properties
  • url, readyState (CONNECTING = 0, OPEN = 1, CLOSING = 2, CLOSED = 3)
  • bufferedAmount (bytes queued but not yet sent — counts data frame payload bytes)
  • protocol, extensions (populated from the handshake response)
  • binaryType ('blob' or 'arraybuffer', default 'blob')
  • Static constants WebSocket.CONNECTING etc.
• Methods
  • send(data) accepting string, ArrayBuffer, ArrayBufferView, Blob
  • Throws InvalidStateError if called while CONNECTING
  • close(code?, reason?) — code must be 1000 or 3000–4999, reason ≤ 123 UTF-8 bytes
• Event handlers
  • onopen, onmessage, onerror, onclose plus addEventListener equivalents
  • MessageEvent data is string, ArrayBuffer, or Blob depending on binaryType
  • CloseEvent with code, reason, wasClean
• Event loop integration
  • The main event loop polls the we-net WebSocket channels each tick and dispatches events
  • In Web Workers (Phase 19), the worker's event loop does the same
• Lifecycle
  • GC root the WebSocket while it has an active connection or queued data, so a created-but-unreferenced WebSocket stays alive

Acceptance Criteria#

• const ws = new WebSocket('wss://...'); ws.onopen = ... dispatches open after the handshake completes
• Sending strings, ArrayBuffers, and Uint8Arrays round-trips against an echo server
• binaryType = 'arraybuffer' causes inbound binary messages to be delivered as ArrayBuffer (instead of Blob)
• ws.close(1000, 'bye') triggers the close handshake and a close event with wasClean: true
• A server-initiated close delivers a close event with the server's status code and reason
• WebSocket usable inside a DedicatedWorkerGlobalScope
• Memory: a new WebSocket(url) without further references is not GC'd before the connection closes
• Unit tests + an integration test that runs a tiny in-process WebSocket server (using the protocol crate's primitives) and verifies the JS side
• Conventions
  • cargo fmt --all --check
  • cargo clippy --workspace -- -D warnings
  • cargo test --workspace