feat(chat): allow knowledge chat before upload

apps/chat/services.py

@@ -28,6 +28,23 @@ def create_conversation_for_batch(batch_id: str, product_name: str) -> Conversat
     return conversation
 
 
+def create_knowledge_conversation() -> Conversation:
+    """
+    创建未绑定资料包的知识库问答会话。
+
+    该会话用于用户尚未上传资料时直接向 RAG 知识库提问，
+    因此 batch_id 与 product_name 保持为空，Agent Core 通过空范围执行全局检索。
+    """
+    return Conversation.objects.create(
+        conversation_id=_generate_conversation_id(),
+        title="知识库问答会话",
+        product_name="",
+        batch_id="",
+        task_status=Conversation.STATUS_PENDING,
+        node_results=_build_knowledge_node_results(),
+    )
+
+
 def execute_conversation_agent(
     *,
     conversation: Conversation,
@@ -132,6 +149,14 @@ def _build_initial_node_results() -> list[dict]:
     ]
 
 
+def _build_knowledge_node_results() -> list[dict]:
+    return [
+        {"code": "knowledge_retrieval", "label": "知识库检索", "status": "待处理"},
+        {"code": "answer_generation", "label": "问答生成", "status": "待处理"},
+        {"code": "risk", "label": "风险预警", "status": "待处理"},
+    ]
+
+
 def _persist_notification_records(result: AgentResult, *, web_detail_url: str = "") -> None:
     payload = result.notification_payload or {}
     owners = payload.get("owners") or []