feat(backend): AI 反问澄清预检端点——refine 侧结构化 clarify（WFW-9 M1，路线A 两阶段）

润色「再沟通」意见含糊时先反问给选项（路线A：问题走独立非流式 JSON 预检端点，正文仍走
既有 refine 一字不改）。新增：
- ClarifyDecision/ClarifyQuestion/ClarifyOption 结构化 schema（既有 output-schema 处，供
  producer 与端点共用）；clarify_refine.md 教条（含糊→need_clarification+≤1问+2–4锚定选项+
  自由输入；明确→verification 放行；防循环）；注册 clarify_refine_spec(analyst 档,#24)+
  SCHEMA_CATALOG + 重生成金标准。
- clarify_node：build_clarify_request 纯函数(缓存前缀不含易变) + run_clarify（gateway.run
  结构化，判别/校验失败确定性回退 need_clarification=false，只读不写库）。
- POST /projects/{id}/chapters/{no}/refine/clarify → ClarifyDecision（analyst 网关，404/503，
  末尾 commit 记账）。**既有 refine 端点/RefineRequest/Response 完全未改**。
门禁绿：ruff/mypy 227/pytest 900(+test_clarify_spec/_node/style clarify)/alembic 无漂移。

apps/api/tests/test_style.py

@@ -59,10 +59,12 @@ def _app_with_overrides(
     session_factory: FakeSessionFactory | None = None,
     extract_gateway: object | None = None,
     refine_gateway: object | None = None,
+    clarify_gateway: object | None = None,
 ) -> FastAPI:
     os.environ.setdefault("CREDENTIAL_ENC_KEY", Fernet.generate_key().decode())
     from ww_api.main import create_app
     from ww_api.services.project_deps import (
+        get_clarify_gateway,
         get_job_repo,
         get_project_repo,
         get_refine_gateway,
@@ -85,6 +87,8 @@ def _app_with_overrides(
         app.dependency_overrides[get_style_extract_gateway] = lambda: extract_gateway
     if refine_gateway is not None:
         app.dependency_overrides[get_refine_gateway] = lambda: refine_gateway
+    if clarify_gateway is not None:
+        app.dependency_overrides[get_clarify_gateway] = lambda: clarify_gateway
     return app
 
 
@@ -394,3 +398,134 @@ async def test_refine_without_credentials_503() -> None:
     assert resp.status_code == 503
     assert resp.json()["error"]["code"] == ErrorCode.LLM_UNAVAILABLE
     assert session.commits == 0
+
+
+# ---- POST /refine/clarify（润色预检澄清）----
+
+
+def _need_clarification() -> object:
+    from ww_agents import ClarifyDecision, ClarifyOption, ClarifyQuestion
+
+    return ClarifyDecision(
+        need_clarification=True,
+        questions=[
+            ClarifyQuestion(
+                question="你想让这段更有张力，是指哪种方向？",
+                options=[
+                    ClarifyOption(label="加快节奏", value="拆短句、压缩铺陈"),
+                    ClarifyOption(label="加重冲突", value="强化人物对立"),
+                ],
+                allow_free_text=True,
+            )
+        ],
+    )
+
+
+def _clear_decision() -> object:
+    from ww_agents import ClarifyDecision
+
+    return ClarifyDecision(
+        need_clarification=False,
+        verification="我会把被字句改成主动句，其余不动，对吗？",
+    )
+
+
+@pytest.mark.asyncio
+async def test_clarify_returns_need_clarification_and_commits() -> None:
+    project_repo = FakeProjectRepo()
+    pid = await _seed_project(project_repo)
+    session = FakeSession()
+    gateway = FakeReviewGateway(parsed=_need_clarification())
+    app = _app_with_overrides(project_repo=project_repo, session=session, clarify_gateway=gateway)
+
+    async with _client(app) as client:
+        resp = await client.post(
+            f"/projects/{pid}/chapters/1/refine/clarify",
+            json={"segment": "原始段落。", "instruction": "更有张力"},
+        )
+
+    assert resp.status_code == 200
+    body = resp.json()
+    assert body["need_clarification"] is True
+    assert len(body["questions"]) == 1
+    assert body["questions"][0]["options"][0]["label"] == "加快节奏"
+    assert body["questions"][0]["allow_free_text"] is True
+    # analyst 档 + 末尾 commit（记账落库）；指令折进输入文本。
+    assert gateway.requests[0].tier == "analyst"
+    assert session.commits == 1
+    assert "更有张力" in str(gateway.requests[0].input)
+
+
+@pytest.mark.asyncio
+async def test_clarify_returns_clear_decision_read_only() -> None:
+    project_repo = FakeProjectRepo()
+    pid = await _seed_project(project_repo)
+    session = FakeSession()
+    gateway = FakeReviewGateway(parsed=_clear_decision())
+    app = _app_with_overrides(project_repo=project_repo, session=session, clarify_gateway=gateway)
+
+    async with _client(app) as client:
+        resp = await client.post(
+            f"/projects/{pid}/chapters/2/refine/clarify",
+            json={"segment": "把这句的被字句改成主动句。", "instruction": ""},
+        )
+
+    assert resp.status_code == 200
+    body = resp.json()
+    assert body["need_clarification"] is False
+    assert body["questions"] == []
+    assert body["verification"] is not None
+    # 只读不写库：无写侧 repo 参与，仅一次 commit 落网关 usage（不变量 #3）。
+    assert session.commits == 1
+    assert session.rollbacks == 0
+
+
+@pytest.mark.asyncio
+async def test_clarify_unknown_project_404() -> None:
+    app = _app_with_overrides(
+        project_repo=FakeProjectRepo(),
+        clarify_gateway=FakeReviewGateway(parsed=_clear_decision()),
+    )
+    async with _client(app) as client:
+        resp = await client.post(
+            f"/projects/{uuid.uuid4()}/chapters/1/refine/clarify",
+            json={"segment": "原段", "instruction": "x"},
+        )
+    assert resp.status_code == 404
+    assert resp.json()["error"]["code"] == ErrorCode.NOT_FOUND
+
+
+@pytest.mark.asyncio
+async def test_clarify_empty_segment_422() -> None:
+    project_repo = FakeProjectRepo()
+    pid = await _seed_project(project_repo)
+    app = _app_with_overrides(
+        project_repo=project_repo, clarify_gateway=FakeReviewGateway(parsed=_clear_decision())
+    )
+    async with _client(app) as client:
+        resp = await client.post(f"/projects/{pid}/chapters/1/refine/clarify", json={"segment": ""})
+    assert resp.status_code == 422
+
+
+@pytest.mark.asyncio
+async def test_clarify_without_credentials_503() -> None:
+    project_repo = FakeProjectRepo()
+    pid = await _seed_project(project_repo)
+    session = FakeSession()
+
+    async def _no_creds() -> object:
+        raise AppError(ErrorCode.LLM_UNAVAILABLE, "未配置凭据", {"provider": "deepseek"})
+
+    app = _app_with_overrides(project_repo=project_repo, session=session)
+    from ww_api.services.project_deps import get_clarify_gateway
+
+    app.dependency_overrides[get_clarify_gateway] = _no_creds
+
+    async with _client(app) as client:
+        resp = await client.post(
+            f"/projects/{pid}/chapters/1/refine/clarify", json={"segment": "原段"}
+        )
+
+    assert resp.status_code == 503
+    assert resp.json()["error"]["code"] == ErrorCode.LLM_UNAVAILABLE
+    assert session.commits == 0