fix(chain): 修评审 CRITICAL+HIGH — 链网关按 session 重建/日志脱敏/resume 原子化+所有权/死导入

- CRITICAL #1：链 write/review 节点经 gateway_builder 按节点自建 session 现建网关，
  usage_ledger sink 绑活 session，随节点 commit 持久化；run_chain_job 不再转发请求网关
  （其 session 在 BackgroundTask 跑时已关闭，记账行被静默丢弃）。新增 get_chain_gateway_builder
  缝（仿 digest builder），get_chain_gateway 退化为纯 503 凭据预检。守不变量 #1。
- HIGH #2：chain_runner 失败日志不再记 str(exc)（可能含 key/连接串/LLM 输出），改记
  _classify_job_error 脱敏文案 + exc_type（设计 §5）。
- HIGH #3：resume 端点原子抢占 awaiting→running（JobRepo.claim_awaiting_to_running 条件
  UPDATE），抢不到 → 409，防并发 resume 双 Command(resume) 损坏图。
- HIGH #4：resume 校验 job.project_id == project_id（JobView 新增 project_id），不匹配 → 404。
- HIGH #5：resume 返回新 ChainResumeAccepted{job_id,chain_key}，去掉无意义哨兵 start/count=0。
- HIGH #6：删 nodes.py 死导入 extract_conflicts（import + __all__）。
- 测试 #7：e2e 断言链跑后 usage_ledger 有行（#1 回归守卫）+ chapter_reviews 每章一行；
  新增 claim 原子抢占单测 + resume 跨项目 404 / 并发 409 端点测。

apps/api/ww_api/routers/chain.py

@@ -28,6 +28,7 @@ from ww_shared import AppError, ErrorCode, ErrorEnvelope
 
 from ww_api.logging_config import get_logger
 from ww_api.schemas.chain import (
+    ChainResumeAccepted,
     ChainResumeRequest,
     ChainRunAccepted,
     ChainRunRequest,
@@ -44,8 +45,10 @@ from ww_api.services.chain_runner import (
 from ww_api.services.credentials import STUB_OWNER_ID
 from ww_api.services.foreshadow_scan import SessionFactory
 from ww_api.services.project_deps import (
+    GatewayChainBuilder,
     GatewayDigestBuilder,
     get_chain_gateway,
+    get_chain_gateway_builder,
     get_digest_gateway_builder,
     get_job_repo,
     get_project_repo,
@@ -66,6 +69,7 @@ SessionDep = Annotated[AsyncSession, Depends(get_session)]
 SessionFactoryDep = Annotated[SessionFactory, Depends(get_session_factory)]
 CheckpointerFactoryDep = Annotated[CheckpointerFactory, Depends(get_checkpointer_factory)]
 DigestBuilderDep = Annotated[GatewayDigestBuilder, Depends(get_digest_gateway_builder)]
+ChainBuilderDep = Annotated[GatewayChainBuilder, Depends(get_chain_gateway_builder)]
 
 _RUN_ERRORS: dict[int | str, dict[str, Any]] = {
     404: {"model": ErrorEnvelope, "description": "项目或链 key 不存在"},
@@ -97,11 +101,12 @@ async def run_chain(
     background_tasks: BackgroundTasks,
     project_repo: ProjectRepoDep,
     job_repo: JobRepoDep,
-    gateway: ChainGatewayDep,  # 凭据探测（无凭据 → dep 解析阶段 503）
+    gateway: ChainGatewayDep,  # 凭据探测（无凭据 → dep 解析阶段 503）；不用于实际 LLM 调用
     session: SessionDep,
     session_factory: SessionFactoryDep,
     checkpointer_factory: CheckpointerFactoryDep,
     digest_gateway_builder: DigestBuilderDep,
+    chain_gateway_builder: ChainBuilderDep,
 ) -> ChainRunAccepted:
     """发起多章链：写一行 job 返 202，链经 BackgroundTask 异步跑。
 
@@ -132,7 +137,7 @@ async def run_chain(
         chain_key=chain_key,
         start_chapter_no=body.start_chapter_no,
         count=body.count,
-        gateway=gateway,
+        chain_gateway_builder=chain_gateway_builder,
         checkpointer_ctx=checkpointer_factory,
         accept_op=accept_op,
         chapter_repo_factory=_chapter_repo_factory,
@@ -172,22 +177,26 @@ async def resume_chain(
     background_tasks: BackgroundTasks,
     project_repo: ProjectRepoDep,
     job_repo: JobRepoDep,
-    gateway: ChainGatewayDep,
+    gateway: ChainGatewayDep,  # 凭据探测（无凭据 → dep 解析阶段 503）；不用于实际 LLM 调用
     session: SessionDep,
     session_factory: SessionFactoryDep,
     checkpointer_factory: CheckpointerFactoryDep,
     digest_gateway_builder: DigestBuilderDep,
-) -> ChainRunAccepted:
+    chain_gateway_builder: ChainBuilderDep,
+) -> ChainResumeAccepted:
     """裁决续跑：仅当 job=awaiting_input，带裁决经 BackgroundTask resume。
 
-    项目不存在 → 404；job 不存在 → 404；非 awaiting 态 → 409（CONFLICT）。
-    resume 经 `Command(resume=decisions)` 从 interrupt 续跑（同 thread_id=job_id）。
+    项目不存在 → 404；job 不存在 / 不属于该项目 → 404（同案，不枚举）；非 awaiting 态 →
+    409（CONFLICT）。`awaiting→running` 在 HTTP 处理器内**原子抢占**（条件 UPDATE），避免两个
+    并发 resume 都过守卫后双 `Command(resume=...)` 损坏图（审评 #3）；抢不到（已被并发抢走/非
+    awaiting）→ 409。resume 经 `Command(resume=decisions)` 从 interrupt 续跑（同 thread_id）。
     """
     request_id = getattr(request.state, "request_id", None)
 
     await _require_project(project_repo, project_id)
     job = await job_repo.get(job_id)
-    if job is None:
+    # 所有权校验（审评 #4）：job 不存在 **或** 不属于该项目 → 404（同案，避免跨项目枚举 job）。
+    if job is None or job.project_id != project_id:
         raise AppError(ErrorCode.NOT_FOUND, f"job not found: {job_id}")
     if job.status != STATUS_AWAITING:
         raise AppError(
@@ -196,6 +205,17 @@ async def resume_chain(
             {"job_status": job.status},
         )
 
+    # 原子抢占 awaiting→running（审评 #3）：抢不到（并发竞态/已非 awaiting）→ 409，绝不调度。
+    claimed = await job_repo.claim_awaiting_to_running(job_id)
+    await session.commit()  # 抢占须在 202 返回前持久化（防并发 resume 双调度）。
+    if claimed is None:
+        raise AppError(
+            ErrorCode.CONFLICT,
+            f"job {job_id} 已被并发续跑抢占或非 awaiting_input 态，不可重复续跑",
+        )
+
+    chain_key = claimed.kind if claimed.kind in SUPPORTED_CHAINS else "draft_volume"
+
     accept_op = build_accept_op(
         session_factory=session_factory,
         digest_gateway_builder=digest_gateway_builder,
@@ -207,10 +227,10 @@ async def resume_chain(
         job_id,
         project_id=project_id,
         user_id=STUB_OWNER_ID,
-        chain_key=job.kind if job.kind in SUPPORTED_CHAINS else "draft_volume",
+        chain_key=chain_key,
         start_chapter_no=1,  # resume 不重置区间：图从检查点续，初值不再使用。
         count=1,
-        gateway=gateway,
+        chain_gateway_builder=chain_gateway_builder,
         checkpointer_ctx=checkpointer_factory,
         accept_op=accept_op,
         chapter_repo_factory=_chapter_repo_factory,
@@ -227,12 +247,7 @@ async def resume_chain(
         decision_count=len(body.decisions),
     )
     response.status_code = 202
-    return ChainRunAccepted(
-        job_id=job_id,
-        chain_key="draft_volume",
-        start_chapter_no=0,
-        count=0,
-    )
+    return ChainResumeAccepted(job_id=job_id, chain_key=chain_key)
 
 
 def _chapter_repo_factory(session: AsyncSession) -> object: