feat(persistence): add SQLAlchemy 2.0 async ORM scaffold

Introduce a unified database configuration (DatabaseConfig) that
controls both the LangGraph checkpointer and the DeerFlow application
persistence layer from a single `database:` config section.

New modules:
- deerflow.config.database_config — Pydantic config with memory/sqlite/postgres backends
- deerflow.persistence — async engine lifecycle, DeclarativeBase with to_dict mixin, Alembic skeleton
- deerflow.runtime.runs.store — RunStore ABC + MemoryRunStore implementation

Gateway integration initializes/tears down the persistence engine in
the existing langgraph_runtime() context manager. Legacy checkpointer
config is preserved for backward compatibility.

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

backend/packages/harness/deerflow/runtime/runs/store/__init__.py

@@ -0,0 +1,4 @@
+from deerflow.runtime.runs.store.base import RunStore
+from deerflow.runtime.runs.store.memory import MemoryRunStore
+
+__all__ = ["MemoryRunStore", "RunStore"]

backend/packages/harness/deerflow/runtime/runs/store/base.py

@@ -0,0 +1,59 @@
+"""Abstract interface for run metadata storage.
+
+RunManager depends on this interface. Implementations:
+- MemoryRunStore: in-memory dict (development, tests)
+- Future: RunRepository backed by SQLAlchemy ORM
+
+All methods accept an optional owner_id for user isolation.
+When owner_id is None, no user filtering is applied (single-user mode).
+"""
+
+from __future__ import annotations
+
+import abc
+from typing import Any
+
+
+class RunStore(abc.ABC):
+    @abc.abstractmethod
+    async def put(
+        self,
+        run_id: str,
+        *,
+        thread_id: str,
+        assistant_id: str | None = None,
+        owner_id: str | None = None,
+        status: str = "pending",
+        multitask_strategy: str = "reject",
+        metadata: dict[str, Any] | None = None,
+        kwargs: dict[str, Any] | None = None,
+        error: str | None = None,
+        created_at: str | None = None,
+    ) -> None: ...
+
+    @abc.abstractmethod
+    async def get(self, run_id: str) -> dict[str, Any] | None: ...
+
+    @abc.abstractmethod
+    async def list_by_thread(
+        self,
+        thread_id: str,
+        *,
+        owner_id: str | None = None,
+        limit: int = 100,
+    ) -> list[dict[str, Any]]: ...
+
+    @abc.abstractmethod
+    async def update_status(
+        self,
+        run_id: str,
+        status: str,
+        *,
+        error: str | None = None,
+    ) -> None: ...
+
+    @abc.abstractmethod
+    async def delete(self, run_id: str) -> None: ...
+
+    @abc.abstractmethod
+    async def list_pending(self, *, before: str | None = None) -> list[dict[str, Any]]: ...

backend/packages/harness/deerflow/runtime/runs/store/memory.py

@@ -0,0 +1,69 @@
+"""In-memory RunStore. Used when database.backend=memory (default) and in tests.
+
+Equivalent to the original RunManager._runs dict behavior.
+"""
+
+from __future__ import annotations
+
+from datetime import UTC, datetime
+from typing import Any
+
+from deerflow.runtime.runs.store.base import RunStore
+
+
+class MemoryRunStore(RunStore):
+    def __init__(self) -> None:
+        self._runs: dict[str, dict[str, Any]] = {}
+
+    async def put(
+        self,
+        run_id,
+        *,
+        thread_id,
+        assistant_id=None,
+        owner_id=None,
+        status="pending",
+        multitask_strategy="reject",
+        metadata=None,
+        kwargs=None,
+        error=None,
+        created_at=None,
+    ):
+        now = datetime.now(UTC).isoformat()
+        self._runs[run_id] = {
+            "run_id": run_id,
+            "thread_id": thread_id,
+            "assistant_id": assistant_id,
+            "owner_id": owner_id,
+            "status": status,
+            "multitask_strategy": multitask_strategy,
+            "metadata": metadata or {},
+            "kwargs": kwargs or {},
+            "error": error,
+            "created_at": created_at or now,
+            "updated_at": now,
+        }
+
+    async def get(self, run_id):
+        return self._runs.get(run_id)
+
+    async def list_by_thread(self, thread_id, *, owner_id=None, limit=100):
+        results = [r for r in self._runs.values() if r["thread_id"] == thread_id and (owner_id is None or r.get("owner_id") == owner_id)]
+        results.sort(key=lambda r: r["created_at"], reverse=True)
+        return results[:limit]
+
+    async def update_status(self, run_id, status, *, error=None):
+        if run_id in self._runs:
+            self._runs[run_id]["status"] = status
+            if error is not None:
+                self._runs[run_id]["error"] = error
+            self._runs[run_id]["updated_at"] = datetime.now(UTC).isoformat()
+
+    async def delete(self, run_id):
+        self._runs.pop(run_id, None)
+
+    async def list_pending(self, *, before=None):
+        now = before or datetime.now(UTC).isoformat()
+        results = [r for r in self._runs.values() if r["status"] == "pending" and r["created_at"] <= now]
+        results.sort(key=lambda r: r["created_at"])
+        return results