feat(api): Introduce workflow pause state management (#27298)

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

api/core/workflow/graph_events/graph.py

@@ -1,5 +1,6 @@
 from pydantic import Field
 
+from core.workflow.entities.pause_reason import PauseReason
 from core.workflow.graph_events import BaseGraphEvent
 
 
@@ -44,7 +45,8 @@ class GraphRunAbortedEvent(BaseGraphEvent):
 class GraphRunPausedEvent(BaseGraphEvent):
     """Event emitted when a graph run is paused by user command."""
 
-    reason: str | None = Field(default=None, description="reason for pause")
+    # reason: str | None = Field(default=None, description="reason for pause")
+    reason: PauseReason = Field(..., description="reason for pause")
     outputs: dict[str, object] = Field(
         default_factory=dict,
         description="Outputs available to the client while the run is paused.",

api/core/workflow/graph_events/node.py

@@ -5,6 +5,7 @@ from pydantic import Field
 
 from core.rag.entities.citation_metadata import RetrievalSourceMetadata
 from core.workflow.entities import AgentNodeStrategyInit
+from core.workflow.entities.pause_reason import PauseReason
 
 from .base import GraphNodeEventBase
 
@@ -54,4 +55,4 @@ class NodeRunRetryEvent(NodeRunStartedEvent):
 
 
 class NodeRunPauseRequestedEvent(GraphNodeEventBase):
-    reason: str | None = Field(default=None, description="Optional pause reason")
+    reason: PauseReason = Field(..., description="pause reason")