refactor: simplify message tool turn tracking to a single boolean flag

nanobot/agent/loop.py

@@ -383,19 +383,9 @@ class AgentLoop:
                             tools_used=tools_used if tools_used else None)
         self.sessions.save(session)
 
-        suppress_final_reply = False
         if message_tool := self.tools.get("message"):
-            if isinstance(message_tool, MessageTool):
-                sent_targets = set(message_tool.get_turn_sends())
-                suppress_final_reply = (msg.channel, msg.chat_id) in sent_targets
-
-        if suppress_final_reply:
-            logger.info(
-                "Skipping final auto-reply because message tool already sent to {}:{} in this turn",
-                msg.channel,
-                msg.chat_id,
-            )
-            return None
+            if isinstance(message_tool, MessageTool) and message_tool._sent_in_turn:
+                return None
 
         return OutboundMessage(
             channel=msg.channel,