CultMeshLocalServer.start bound TCP to port 0 and then bound UDP to whatever number
the kernel picked, failing with EADDRINUSE whenever another process held that
number for UDP (this host has hundreds of UDP listeners), and left the accept
thread running on failure. Port 0 now retries with a fresh pair (bounded); both
sockets bind before any thread starts; an explicit port still fails honestly.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
