style: apply ruff format to persistence and runtime files

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/packages/harness/deerflow/persistence/engine.py

@@ -20,6 +20,7 @@ def _json_serializer(obj: object) -> str:
     """JSON serializer with ensure_ascii=False for Chinese character support."""
     return json.dumps(obj, ensure_ascii=False)
 
+
 logger = logging.getLogger(__name__)
 
 _engine: AsyncEngine | None = None

backend/packages/harness/deerflow/persistence/migrations/env.py

@@ -21,10 +21,7 @@ try:
     import deerflow.persistence.models  # noqa: F401 — register ORM models with Base.metadata
 except ImportError:
     # Models not available — migration will work with existing metadata only.
-    logging.getLogger(__name__).warning(
-        "Could not import deerflow.persistence.models; "
-        "Alembic may not detect all tables"
-    )
+    logging.getLogger(__name__).warning("Could not import deerflow.persistence.models; Alembic may not detect all tables")
 
 config = context.config
 if config.config_file_name is not None:

backend/packages/harness/deerflow/persistence/repositories/thread_meta_repo.py

@@ -99,11 +99,7 @@ class ThreadMetaRepository:
     async def update_display_name(self, thread_id: str, display_name: str) -> None:
         """Update the display_name (title) for a thread."""
         async with self._sf() as session:
-            await session.execute(
-                update(ThreadMetaRow)
-                .where(ThreadMetaRow.thread_id == thread_id)
-                .values(display_name=display_name, updated_at=datetime.now(UTC))
-            )
+            await session.execute(update(ThreadMetaRow).where(ThreadMetaRow.thread_id == thread_id).values(display_name=display_name, updated_at=datetime.now(UTC)))
             await session.commit()
 
     async def update_status(self, thread_id: str, status: str) -> None: