Nitpick: Calling send_data on socket in draining state should result in `{error,closed}`

[essen]

In v1.3.0 it returns in {error, {invalid_state, draining}}. I think it should return {error, closed} because we can try to send data under normal conditions before we could process the message telling us about the socket close. The same is probably true of most functions called during the draining state.

=SUPERVISOR REPORT==== 27-Apr-2026::12:22:22.259969 ===
    supervisor: {<0.335.0>,corral_conns_sup}
    errorContext: child_terminated
    reason: {{case_clause,{error,{invalid_state,draining}}},
             [{corral_echo_protocol,handle,2,
                                    [{file,"test/corral_echo_protocol.erl"},
                                     {line,125}]},
              {proc_lib,init_p_do_apply,3,
                        [{file,"proc_lib.erl"},{line,333}]}]}
    offender: [{pid,<0.342.0>},
               {id,corral_echo_protocol},
               {mfargs,
                   {corral_echo_protocol,start_link,
                       [do_stop_sending_server_test,corral_quic,<0.341.0>,
                        opts]}},
               {restart_type,permanent},
               {significant,false},
               {shutdown,5000},
               {child_type,worker}]