feat(graph_engine): add ready_queue state persistence to GraphRuntimeState

- Add ReadyQueueState TypedDict for type-safe queue serialization
- Add ready_queue attribute to GraphRuntimeState for initializing with pre-existing queue state
- Update GraphEngine to load ready_queue from GraphRuntimeState on initialization
- Implement proper type hints using ReadyQueueState for better type safety
- Add comprehensive tests for ready_queue loading functionality

The ready_queue is read-only after initialization and allows resuming workflow
execution with a pre-populated queue of nodes ready to execute.

api/core/workflow/entities/graph_runtime_state.py

@@ -1,5 +1,5 @@
 from copy import deepcopy
-from typing import Any
+from typing import TYPE_CHECKING, Any
 
 from pydantic import BaseModel, PrivateAttr
 
@@ -7,6 +7,9 @@ from core.model_runtime.entities.llm_entities import LLMUsage
 
 from .variable_pool import VariablePool
 
+if TYPE_CHECKING:
+    from core.workflow.graph_engine.ready_queue import ReadyQueueState
+
 
 class GraphRuntimeState(BaseModel):
     # Private attributes to prevent direct modification
@@ -16,6 +19,7 @@ class GraphRuntimeState(BaseModel):
     _llm_usage: LLMUsage = PrivateAttr(default_factory=LLMUsage.empty_usage)
     _outputs: dict[str, Any] = PrivateAttr(default_factory=dict)
     _node_run_steps: int = PrivateAttr(default=0)
+    _ready_queue: "ReadyQueueState | dict[str, object]" = PrivateAttr(default_factory=dict)
 
     def __init__(
         self,
@@ -25,6 +29,7 @@ class GraphRuntimeState(BaseModel):
         llm_usage: LLMUsage | None = None,
         outputs: dict[str, Any] | None = None,
         node_run_steps: int = 0,
+        ready_queue: "ReadyQueueState | dict[str, object] | None" = None,
         **kwargs: object,
     ):
         """Initialize the GraphRuntimeState with validation."""
@@ -51,6 +56,10 @@ class GraphRuntimeState(BaseModel):
             raise ValueError("node_run_steps must be non-negative")
         self._node_run_steps = node_run_steps
 
+        if ready_queue is None:
+            ready_queue = {}
+        self._ready_queue = deepcopy(ready_queue)
+
     @property
     def variable_pool(self) -> VariablePool:
         """Get the variable pool."""
@@ -133,3 +142,8 @@ class GraphRuntimeState(BaseModel):
         if tokens < 0:
             raise ValueError("tokens must be non-negative")
         self._total_tokens += tokens
+
+    @property
+    def ready_queue(self) -> "ReadyQueueState | dict[str, object]":
+        """Get a copy of the ready queue state."""
+        return deepcopy(self._ready_queue)