MessageTool writes to session; remove max_messages limit

- MessageTool now writes sent messages to session history via SessionManager
- Agent loop wires SessionManager into MessageTool constructor
- Session.get_history() returns full history (removed max_messages limit)
  Server-side context editing API handles trimming, so we send full history

This ensures messages sent via the message() tool (e.g., from heartbeat forks)
are visible in the main conversational agent's context.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

nanobot/agent/loop.py

@@ -119,7 +119,7 @@ class AgentLoop:
         self.tools.register(WebFetchTool())
         
         # Message tool
-        message_tool = MessageTool(send_callback=self.bus.publish_outbound)
+        message_tool = MessageTool(send_callback=self.bus.publish_outbound, sessions=self.sessions)
         self.tools.register(message_tool)
         
         # Spawn tool (for subagents)

nanobot/agent/tools/message.py

@@ -4,6 +4,7 @@ from typing import Any, Awaitable, Callable
 
 from nanobot.agent.tools.base import Tool
 from nanobot.bus.events import OutboundMessage
+from nanobot.session import SessionManager
 
 
 class MessageTool(Tool):
@@ -12,11 +13,13 @@ class MessageTool(Tool):
     def __init__(
         self,
         send_callback: Callable[[OutboundMessage], Awaitable[None]] | None = None,
+        sessions: SessionManager | None = None,
         default_channel: str = "",
         default_chat_id: str = "",
         default_message_id: str | None = None,
     ):
         self._send_callback = send_callback
+        self._sessions = sessions
         self._default_channel = default_channel
         self._default_chat_id = default_chat_id
         self._default_message_id = default_message_id
@@ -101,6 +104,13 @@ class MessageTool(Tool):
 
         try:
             await self._send_callback(msg)
+
+            if self._sessions:
+                session_key = f"{channel}:{chat_id}"
+                session = self._sessions.get_or_create(session_key)
+                session.add_message("assistant", content)
+                self._sessions.save(session)
+
             if channel == self._default_channel and chat_id == self._default_chat_id:
                 self._sent_in_turn = True
             media_info = f" with {len(media)} attachments" if media else ""