fix: skip system-injected user messages, only send real user query to Antaf

The xiaozhi server injects tool_call reminders and system prompts as
role=user messages into dialogue. These were being picked up as the
"last user message" and sent to Antaf bridge instead of the actual query.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/main/xiaozhi-server/core/providers/llm/antaf/antaf.py

@@ -36,13 +36,33 @@ class LLMProvider(LLMProviderBase):
                 return True
         return False
 
+    @staticmethod
+    def _is_system_injected(content):
+        """检测是否为系统注入的消息（非用户真实输入）"""
+        if not content:
+            return True
+        markers = [
+            "[系统提示]", "tool_call", "<tool_call>", "TOOL USE",
+            "系统提示", "工具调用", "function_call",
+            "handle_exit_intent", "你有以下工具", "You have access",
+        ]
+        for m in markers:
+            if m in content:
+                return True
+        # 超过200字的 user 消息大概率是系统注入的
+        if len(content) > 200:
+            return True
+        return False
+
     def response(self, session_id, dialogue, **kwargs):
-        # 提取最后一条用户消息
+        # 从 dialogue 中提取真正的用户消息（跳过系统注入的 user 消息）
         query = ""
         for msg in reversed(dialogue):
             if msg.get("role") == "user":
-                query = msg.get("content", "")
-                break
+                content = msg.get("content", "")
+                if not self._is_system_injected(content):
+                    query = content
+                    break
 
         if not query:
             logger.bind(tag=TAG).warning("对话中没有用户消息")