feat(sync): export edge artifact authority model

core/sync/__init__.py

@@ -0,0 +1,19 @@
+"""Edge/cloud sync contracts for CORE.
+
+This package is intentionally pure at import time: no object-store client,
+no network dependency, and no hot-path integration.
+"""
+
+from core.sync.artifacts import (
+    ARTIFACT_AUTHORITY,
+    ArtifactAuthority,
+    ArtifactType,
+    authority_for,
+)
+
+__all__ = [
+    "ARTIFACT_AUTHORITY",
+    "ArtifactAuthority",
+    "ArtifactType",
+    "authority_for",
+]