[guybedford]

Add net.BoundSocket, a synchronous TCP bind primitive that mirrors POSIX bind(2): the socket is bound to a local address but stays role-agnostic until it is adopted as a server (server.listen()) or a client (new net.Socket({ handle }) followed by connect()).

Constructing a net.BoundSocket binds inline via the existing uv_tcp_bind() path, so the kernel-assigned address (including the ephemeral port when port is 0) is available immediately via boundSocket.address(), and bind errors throw synchronously.

Adoption transfers ownership of the underlying handle; afterwards address() and close() throw ERR_SOCKET_HANDLE_ADOPTED. An un-adopted handle is released with close() or via Symbol.dispose (using).

The handle is passed in-process rather than as a file descriptor, so it also works on Windows.