refactor: inline base64 image stripping in _save_turn

nanobot/agent/loop.py

@@ -463,15 +463,20 @@ class AgentLoop:
     def _save_turn(self, session: Session, messages: list[dict], skip: int) -> None:
         """Save new-turn messages into session, truncating large tool results."""
         from datetime import datetime
-        from nanobot.utils import helpers
         for m in messages[skip:]:
             entry = {k: v for k, v in m.items() if k != "reasoning_content"}
             if entry.get("role") == "tool" and isinstance(entry.get("content"), str):
                 content = entry["content"]
                 if len(content) > self._TOOL_RESULT_MAX_CHARS:
-                    entry["content"] = content[: self._TOOL_RESULT_MAX_CHARS] + "\n... (truncated)"
-            if entry.get("role") == "user":
-                entry["content"] = helpers.strip_base64_images(entry["content"])
+                    entry["content"] = content[:self._TOOL_RESULT_MAX_CHARS] + "\n... (truncated)"
+            if entry.get("role") == "user" and isinstance(entry.get("content"), list):
+                entry["content"] = [
+                    {"type": "text", "text": "[image]"} if (
+                        c.get("type") == "image_url"
+                        and c.get("image_url", {}).get("url", "").startswith("data:image/")
+                    ) else c
+                    for c in entry["content"]
+                ]
             entry.setdefault("timestamp", datetime.now().isoformat())
             session.messages.append(entry)
         session.updated_at = datetime.now()