fix: commit migration role assumption

Assistant: codex
Assistant-Model: gpt-5.6-sol
Assistant-Session: 01a02b22-9638-76d2-bbff-b7ea1770b118

tests/test_database_rotation.py

@@ -5,6 +5,21 @@ from pathlib import Path
 from sbom_nexus import database
 
 
+def test_migration_role_commits_autobegin_before_alembic_transaction() -> None:
+    events: list[str] = []
+
+    class Connection:
+        def exec_driver_sql(self, statement: str) -> None:
+            events.append(statement)
+
+        def commit(self) -> None:
+            events.append("COMMIT")
+
+    database.assume_migration_role(Connection(), "sbom_nexus_owner")
+
+    assert events == ['SET ROLE "sbom_nexus_owner"', "COMMIT"]
+
+
 def test_dynamic_connection_factory_rereads_mounted_url(monkeypatch, tmp_path: Path) -> None:
     secret = tmp_path / "url"
     observed: list[str] = []