[NOTICKET][doc] correct metadata key path in _format_context

src/api/v1/chat.py

@@ -52,8 +52,9 @@ def _format_context(results: List[RetrievalResult]) -> str:
     """Format retrieval results as context string for the LLM."""
     lines = []
     for result in results:
-        filename = result.metadata.get("filename", "Unknown")
-        page = result.metadata.get("page_label")
+        data = result.metadata.get("data", {})
+        filename = data.get("filename", "Unknown")
+        page = data.get("page_label")
         source_label = f"{filename}, p.{page}" if page else filename
         lines.append(f"[Source: {source_label}]\n{result.content}\n")
     return "\n".join(lines)