feat(check): 文件要在、扫描件兜底（C10）；响应方式存进清单并可改（C12）

- check/presence.py：「提供《授权委托书》」「须提交投标函」这类要求按标题里有没有这个文件名判断，不调模型。
- 扫描件兜底：要附证明材料的要求没找到、投标文件里有扫描件页时，改为提示级「可能在扫描件里，请人工核对」。
- 响应方式解析时识别、带依据句子存进 checklist.response_modes（迁移 0008）；清单页显示、可改（写审计，
  重新解析不覆盖人工改过的）；查标用存下来的。新接口 PUT /projects/{id}/checklist/response-modes/{category}。
- check_item_result.layer 加 presence（迁移 0007）；契约同步默认接受的两种结论。

开发集 17 份：规矩投标文件的致命问题 120 → 51，致命级召回不变（22 / 32）（docs/architecture/check-eval.md §5）。

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

server/tests/test_check_flow.py

@@ -251,3 +251,24 @@ async def test_other_tenant_cannot_see_check(app_client: httpx.AsyncClient) -> N
     assert (await b.post(f"/findings/{f['id']}/resolve", json={"status": "modified"})).status_code == 404
     assert (await b.post(f"/findings/{f['id']}/reopen")).status_code == 404
     assert (await b.post(f"/check-runs/{run['id']}/cancel")).status_code == 404
+
+
+async def test_response_modes_are_stored_editable_and_used(user: User) -> None:
+    """响应方式（C12）：解析时存进清单；用户改成「默认接受」后，查标对没复述的一般要求不再报问题。"""
+    project_id, tender_id = await project_with_tender(user)
+    await run_parse(user, tender_id)
+    modes = {m["category"]: m for m in (await user.get(f"/projects/{project_id}/checklist")).json()["response_modes"]}
+    assert set(modes) == {"technical", "commercial"}
+    assert modes["technical"]["mode"] == "explicit" and modes["technical"]["status"] == "unknown"
+
+    r = await user.put(f"/projects/{project_id}/checklist/response-modes/technical", json={"mode": "implicit"})
+    assert r.status_code == 200, r.text
+    tech = next(m for m in r.json()["response_modes"] if m["category"] == "technical")
+    assert tech["origin"] == "human" and tech["mode"] == "implicit" and tech["set_by"]["name"] == "张工"
+
+    bid = await upload_bid(user, project_id, "bid-mini-v1.pdf")
+    run = await run_check(user, project_id, [bid["id"]])
+    # 漏掉的 BFD 是 ★ 条款：默认接受下不报致命，改为提示级「请人工核对」
+    (f,) = await findings(user, run["id"])
+    assert f["type"] == "manual_review" and f["severity"] == "hint"
+    assert run["counts"]["fatal"] == 0