feat(validation): add versioned policy planner

Author: zkwentz

src/openenv/cli/_validation.py

@@ -15,6 +15,7 @@
     ValidationSeverity,
     ValidationStatus,
 )
+from .planner import build_validation_plan, VALIDATION_POLICY_VERSION
 from .task_manifest import (
     ArtifactSpec,
     EnvironmentConfig,
@@ -40,6 +41,7 @@
     "TaskIdentity",
     "TaskManifest",
     "TaskManifestLoad",
+    "VALIDATION_POLICY_VERSION",
     "ValidationCapability",
     "ValidationCheck",
     "ValidationContext",
@@ -49,5 +51,6 @@
     "ValidationResult",
     "ValidationSeverity",
     "ValidationStatus",
+    "build_validation_plan",
     "load_task_manifest",
 ]