When a member replies in a member-started thread without @mentioning the
assigned agent, the on_comment trigger was suppressed — even if the agent
had already replied in that thread. This meant the common flow of
"member posts → agent replies → member follows up" would not re-trigger
the agent on the follow-up.
Add HasAgentRepliedInThread SQL query and check it in isReplyToMemberThread
so that agent participation in a thread is treated as an ongoing conversation.