fix: restore Flow execution state from checkpoint fields

Flow.from_checkpoint deserialized the checkpoint_* fields but never
copied them back into the private execution attrs (_completed_methods,
_method_outputs, _method_execution_counts, _state). Calling kickoff()
after from_checkpoint would restart from scratch.

Add _restore_from_checkpoint that copies the checkpoint fields into the
private attrs, using the existing _restore_state method for state
reconstruction.

lib/crewai/src/crewai/flow/flow.py

@@ -941,6 +941,7 @@ class Flow(BaseModel, Generic[T], metaclass=FlowMeta):
             if isinstance(entity, cls):
                 if entity.execution_context is not None:
                     apply_execution_context(entity.execution_context)
+                entity._restore_from_checkpoint()
                 return entity
         raise ValueError(f"No {cls.__name__} found in checkpoint: {path}")
 
@@ -949,6 +950,21 @@ class Flow(BaseModel, Generic[T], metaclass=FlowMeta):
     checkpoint_method_counts: dict[str, int] | None = Field(default=None)
     checkpoint_state: dict[str, Any] | None = Field(default=None)
 
+    def _restore_from_checkpoint(self) -> None:
+        """Restore private execution state from checkpoint fields."""
+        if self.checkpoint_completed_methods is not None:
+            self._completed_methods = {
+                FlowMethodName(m) for m in self.checkpoint_completed_methods
+            }
+        if self.checkpoint_method_outputs is not None:
+            self._method_outputs = list(self.checkpoint_method_outputs)
+        if self.checkpoint_method_counts is not None:
+            self._method_execution_counts = {
+                FlowMethodName(k): v for k, v in self.checkpoint_method_counts.items()
+            }
+        if self.checkpoint_state is not None:
+            self._restore_state(self.checkpoint_state)
+
     _methods: dict[FlowMethodName, FlowMethod[Any, Any]] = PrivateAttr(
         default_factory=dict
     )