Add docs/WebSocketDebugger.md covering the transport, message protocol,
broadcast/request event catalog, how to enable it, LAN discovery, and how
the bundled JS web debugger (assets/debugger submodule) connects to it.
Point AGENTS.md at it so future sessions know it exists.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XDNwPPuidmNxQGRJxBuRL6
