Evidence with supportive metadata

tests/test_storage_migrations.py

@@ -34,6 +34,12 @@ def test_initialize_is_idempotent_and_applies_expected_columns(tmp_path):
 
     assert "source_refs" in feature_columns
     assert "source_refs" in evidence_columns
+    assert {
+        "target_kind",
+        "target_id",
+        "reference_kind",
+        "reference_id",
+    } <= evidence_columns
     assert "content_chunks" in tables
     assert "expectation_gaps" in tables