Add workflow graph validation checks (#27106)

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>

api/core/workflow/entities/__init__.py

@@ -1,3 +1,5 @@
+from ..runtime.graph_runtime_state import GraphRuntimeState
+from ..runtime.variable_pool import VariablePool
 from .agent import AgentNodeStrategyInit
 from .graph_init_params import GraphInitParams
 from .workflow_execution import WorkflowExecution
@@ -6,6 +8,8 @@ from .workflow_node_execution import WorkflowNodeExecution
 __all__ = [
     "AgentNodeStrategyInit",
     "GraphInitParams",
+    "GraphRuntimeState",
+    "VariablePool",
     "WorkflowExecution",
     "WorkflowNodeExecution",
 ]