fix: common prerequisite node workflow remove reachable node that failed to streaming llm… (#19552)

Co-authored-by: zhangshibo <zhangshibo@didiglobal.com>

api/core/workflow/nodes/answer/base_stream_processor.py

@@ -95,7 +95,12 @@ class StreamProcessor(ABC):
         if node_id not in self.rest_node_ids:
             return
 
+        if node_id in reachable_node_ids:
+            return
+
         self.rest_node_ids.remove(node_id)
+        self.rest_node_ids.extend(set(reachable_node_ids) - set(self.rest_node_ids))
+
         for edge in self.graph.edge_mapping.get(node_id, []):
             if edge.target_node_id in reachable_node_ids:
                 continue