perf: SQLite 开 WAL 与写锁等待，支持流水线并发写

批量流水线会在多个线程里同时写产物与进度，默认的回滚日志模式与 5 秒
busy timeout 下容易出现 database is locked。

- 连接统一带 `WOV_DB_BUSY_TIMEOUT_SECONDS`（默认 30 秒）等待写锁。
- 打开 WAL 与 `synchronous=NORMAL`：读写并行，落盘开销更低；不支持 WAL 的
  文件系统会保持原模式（SQLite 自身降级）。
- 测试：断言 WAL 生效，并用 4 线程 × 25 条并发写产物验证不丢数据、不报错。

tests/app/test_db/test_database.py

@@ -381,3 +381,62 @@ def test_recover_interrupted_batch_jobs_requeues_zombie_completed(db_with_workfl
     assert count == 1
     assert db_with_workflow.get_batch_job("zombie")["status"] == "QUEUED"
     assert db_with_workflow.get_batch_job("done")["status"] == "COMPLETED"
+
+
+def test_wal_mode_enabled_for_concurrent_pipeline_writes(tmp_path: Path) -> None:
+    """数据：临时库文件。
+
+    过程：打开一次连接并读取日志模式。
+
+    验证：处于 WAL 模式——批量流水线多线程并发写产物/进度时，读写可并行，
+    不会互相阻塞成 database is locked。
+    """
+    db = Database(tmp_path / "wov.db")
+
+    with db._connect() as conn:
+        mode = conn.execute("PRAGMA journal_mode").fetchone()[0]
+
+    assert mode.lower() == "wal"
+
+
+def test_concurrent_artifact_writes_survive(tmp_path: Path) -> None:
+    """数据：四个线程各自往同一任务写入 25 条产物记录。
+
+    过程：并发调用 create_artifact（批量流水线里多个视频同时落产物的场景）。
+
+    验证：全部写入成功且记录数正确，没有因写锁竞争丢数据或抛异常。
+    """
+    import threading
+
+    db = Database(tmp_path / "wov.db")
+    db.upsert_workflow({"id": "wf", "name": "流程", "description": "", "published": 1, "latest_version": 1})
+    db.create_workflow_version("wf", 1, {"nodes": []})
+    db.create_run({
+        "id": "run-concurrent", "workflow_id": "wf", "workflow_version": 1,
+        "status": "RUNNING", "source": "batch", "created_at": "t1", "updated_at": "t1",
+    })
+    errors: list[Exception] = []
+
+    def writer(worker: int) -> None:
+        try:
+            for index in range(25):
+                db.create_artifact({
+                    "run_id": "run-concurrent", "node_id": "asr",
+                    "name": f"w{worker}-{index}", "uri": f"/tmp/w{worker}-{index}.srt",
+                    "mime_type": "text/plain", "size": index,
+                })
+        except Exception as exc:  # noqa: BLE001 - 用例要报告任意写失败
+            errors.append(exc)
+
+    threads = [threading.Thread(target=writer, args=(n,)) for n in range(4)]
+    for thread in threads:
+        thread.start()
+    for thread in threads:
+        thread.join()
+
+    assert errors == []
+    with db._connect() as conn:
+        count = conn.execute(
+            "SELECT COUNT(*) FROM artifacts WHERE run_id = ?", ("run-concurrent",),
+        ).fetchone()[0]
+    assert count == 100