feat(graph_engine): Support pausing workflow graph executions (#26585)

Signed-off-by: -LAN- <laipz8200@outlook.com>

api/core/workflow/node_events/__init__.py

@@ -14,6 +14,7 @@ from .loop import (
 )
 from .node import (
     ModelInvokeCompletedEvent,
+    PauseRequestedEvent,
     RunRetrieverResourceEvent,
     RunRetryEvent,
     StreamChunkEvent,
@@ -33,6 +34,7 @@ __all__ = [
     "ModelInvokeCompletedEvent",
     "NodeEventBase",
     "NodeRunResult",
+    "PauseRequestedEvent",
     "RunRetrieverResourceEvent",
     "RunRetryEvent",
     "StreamChunkEvent",

api/core/workflow/node_events/node.py

@@ -40,3 +40,7 @@ class StreamChunkEvent(NodeEventBase):
 
 class StreamCompletedEvent(NodeEventBase):
     node_run_result: NodeRunResult = Field(..., description="run result")
+
+
+class PauseRequestedEvent(NodeEventBase):
+    reason: str | None = Field(default=None, description="Optional pause reason")