Extend ipn.listen to also accept "tcp"/"tcp4"/"tcp6" and return a
TCPListener bound to a netstack gonet.TCPListener. The listener
exposes accept/close/addr like a Go net.Listener and additionally
implements Symbol.asyncIterator so JS callers can write:
for await (const conn of listener) { ... }
The async iterator returns done when the listener is closed (via
errors.Is(net.ErrClosed)) and rejects on any other accept error.
Symbol-keyed properties are set via Reflect.set since syscall/js
only exposes string-keyed Set.
codinget
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