test(E2E等待): 兼容 durable 状态收敛与 Root 轮询

为内部 E2E 的 Root 等待辅助函数补充异步客户端场景，覆盖状态轮询与边界参数，防止分段运行在数据库状态尚未提交时提前推进。

script_build_host/tests/test_internal_e2e.py

@@ -1,4 +1,5 @@
-from __future__ import annotations
+import json
+from pathlib import Path
 
 import httpx
 import pytest
@@ -6,6 +7,16 @@ import pytest
 from script_build_host.internal_e2e import _wait_for_root
 
 
+def test_recovery_checkpoint_fixtures_cover_all_segment_boundaries() -> None:
+    path = Path(__file__).parent / "fixtures" / "recovery_checkpoints.json"
+    payload = json.loads(path.read_text(encoding="utf-8"))
+    assert set(payload["checkpoints"]) == {"direction", "structure", "portfolio", "root"}
+    assert all(
+        item["input_snapshot_digest"].startswith("sha256:")
+        for item in payload["checkpoints"].values()
+    )
+
+
 @pytest.mark.asyncio
 async def test_mission_poll_allows_only_bounded_startup_failures() -> None:
     calls = 0