fix: extract content from ASR JSON before sending to Antaf

ASR wraps user speech as JSON {"content":"...", "language":"zh", "emotion":"..."},
extract only the content field instead of sending raw JSON to Antaf bridge.

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

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

@@ -1,3 +1,4 @@
+import json
 import requests
 from config.logger import setup_logging
 from core.providers.llm.base import LLMProviderBase
@@ -61,6 +62,14 @@ class LLMProvider(LLMProviderBase):
             if msg.get("role") == "user":
                 content = msg.get("content", "")
                 if not self._is_system_injected(content):
+                    # ASR 结果可能是 JSON: {"content":"...", "language":"zh", "emotion":"..."}
+                    try:
+                        parsed = json.loads(content)
+                        if isinstance(parsed, dict) and "content" in parsed:
+                            query = parsed["content"]
+                        else:
+                            query = content
+                    except (json.JSONDecodeError, TypeError):
                         query = content
                     break