message/command: use callback API for message responses; switch to time.Duration for Requeue
conn: expose FIN/REQ callbacks; refactor Message response plumbing
reader: remove AsyncHandler interface
conn: fix WriteCommand locking
conn: close read side first, then write; trap conn closed errors
conn: don't publicly embed net.Conn
conn: s/Stop/Close; CloseRead if no messages in flight upon Close(); refactor
conn: refactor WriteCommand locking and simplify Flush
reader: use new conn.Close
reader: use wg for rdyLoop and lookupdLoop; s/ExitChan/StopChan
reader/writer/conn: conn doesn't take topic/channel
reader: add global reader instance counter
reader: consistent exit path for long running handler goroutine
reader/writer/conn: drop individual callbacks for delegate interface
reader: comment fixes; make atomic counters private
reader/conn: un-export embedded sync.RWMutex
reader/writer/conn: log levels and delegates
reader/conn: add requeue without backoff
reader: add HandlerFunc helper interface
message: drop EncodeBytes; s/Write/WriteTo; drop binary.{Read,Write}