refactor(runtime): add run DDD boundary skeleton

backend/packages/harness/deerflow/runtime/runs/domain/errors.py

@@ -0,0 +1,24 @@
+"""Domain-level errors for run lifecycle operations."""
+
+from __future__ import annotations
+
+from .value_objects import RunStatus
+
+
+class RunDomainError(Exception):
+    """Base class for run runtime domain errors."""
+
+
+class InvalidRunTransition(RunDomainError):
+    """Raised when a run status transition violates lifecycle rules."""
+
+    def __init__(self, current: RunStatus, target: RunStatus) -> None:
+        super().__init__(f"Cannot transition run from {current.value!r} to {target.value!r}")
+        self.current = current
+        self.target = target
+
+
+__all__ = [
+    "InvalidRunTransition",
+    "RunDomainError",
+]