feat(agent): 增强多模态链路与工具调用能力

backend/src/v1/agent/repository.py

@@ -107,6 +107,10 @@ class AgentRepository:
             raise HTTPException(status_code=404, detail="Session not found")
 
         next_seq = int(session_row.message_count or 0) + 1
+        if not _has_title(session_row.title):
+            session_title = _derive_session_title(content_text)
+            if session_title is not None:
+                session_row.title = session_title
         payload_metadata = dict(metadata or {})
         payload_metadata["run_id"] = run_id
         message = AgentChatMessage(
@@ -264,3 +268,14 @@ class AgentRepository:
                 if rendered:
                     payload["attachments"] = rendered
         return payload
+
+
+def _has_title(title: object) -> bool:
+    return isinstance(title, str) and bool(title.strip())
+
+
+def _derive_session_title(content_text: str) -> str | None:
+    normalized = " ".join(content_text.split())
+    if not normalized:
+        return None
+    return normalized[:80]