fix: store current_message in session to preserve time prefix for cache hits

session.add_message was storing raw msg.content without the [Current time: ...]
prefix, causing cache key mismatches on subsequent turns since the API received
the prefixed version but history replayed the raw version.

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

nanobot/agent/loop.py

@@ -393,7 +393,9 @@ class AgentLoop:
         logger.info(f"Response to {msg.channel}:{msg.sender_id}: {preview}")
         
         # Save to session (include tool names so consolidation sees what happened)
-        session.add_message("user", msg.content)
+        # Store current_message (not msg.content) so the time prefix is preserved
+        # and cache keys match on subsequent turns
+        session.add_message("user", current_message)
         session.add_message("assistant", final_content,
                             tools_used=tools_used if tools_used else None)
         self.sessions.save(session)