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。

packages/core/tests/test_chain_graph.py

@@ -184,6 +184,10 @@ def _make_harness(*, conflicts: list[Conflict]) -> dict[str, Any]:
         draft_text="第 N 章正文。", conflicts=conflicts, by_schema=_empty_by_schema()
     )
 
+    async def gateway_builder(session: Any) -> Any:
+        """按节点 session 建网关的替身（不变量 #1）：忽略 session，恒返同一 mock 网关。"""
+        return gateway
+
     def memory_repos_factory(session: Any) -> Any:
         return object()  # assemble 被 fake 替换，不实际用 repos
 
@@ -207,6 +211,7 @@ def _make_harness(*, conflicts: list[Conflict]) -> dict[str, Any]:
 
     return {
         "gateway": gateway,
+        "gateway_builder": gateway_builder,
         "session_factory": _session_factory,
         "memory_repos_factory": memory_repos_factory,
         "chapter_repo_factory": chapter_repo_factory,
@@ -221,7 +226,7 @@ def _make_harness(*, conflicts: list[Conflict]) -> dict[str, Any]:
 
 def _build(h: dict[str, Any], checkpointer: Any) -> Any:
     return build_chain_graph(
-        h["gateway"],
+        h["gateway_builder"],
         session_factory=h["session_factory"],
         memory_repos_factory=h["memory_repos_factory"],
         chapter_repo_factory=h["chapter_repo_factory"],
@@ -317,7 +322,7 @@ async def test_write_chapter_saves_collected_draft() -> None:
 
     out = await write_chapter(
         state,
-        gateway=h["gateway"],
+        gateway_builder=h["gateway_builder"],
         session_factory=h["session_factory"],
         memory_repos_factory=h["memory_repos_factory"],
         chapter_repo_factory=h["chapter_repo_factory"],

packages/core/tests/test_job_repo.py

@@ -100,6 +100,14 @@ class FakeJobRepo:
         row.result = dict(result)
         return _view(row)
 
+    async def claim_awaiting_to_running(self, job_id: uuid.UUID) -> JobView | None:
+        """原子抢占 awaiting→running（内存替身：仅当现态 awaiting 才抢到，否则 None）。"""
+        row = next((r for r in self.rows if r.id == job_id), None)
+        if row is None or row.status != STATUS_AWAITING:
+            return None
+        row.status = STATUS_RUNNING
+        return _view(row)
+
     async def fail(self, job_id: uuid.UUID, error: str) -> JobView:
         row = self._require(job_id)
         row.status = STATUS_FAILED
@@ -173,6 +181,39 @@ async def test_fail_sets_failed_and_error() -> None:
     assert failed.error == "boom"
 
 
+# ---- 原子抢占 awaiting → running（防并发 resume 竞态，审评 #3）----
+
+
+async def test_claim_awaiting_to_running_succeeds_once() -> None:
+    repo: JobRepo = _repo()
+    job = await repo.create(PROJECT, KIND)
+    await repo.set_awaiting(job.id, {"awaiting_chapter": 1})
+    claimed = await repo.claim_awaiting_to_running(job.id)
+    assert claimed is not None
+    assert claimed.status == STATUS_RUNNING
+
+
+async def test_claim_awaiting_second_call_returns_none() -> None:
+    repo: JobRepo = _repo()
+    job = await repo.create(PROJECT, KIND)
+    await repo.set_awaiting(job.id, {"awaiting_chapter": 1})
+    first = await repo.claim_awaiting_to_running(job.id)
+    second = await repo.claim_awaiting_to_running(job.id)  # 已 running → 抢不到
+    assert first is not None
+    assert second is None
+
+
+async def test_claim_non_awaiting_returns_none() -> None:
+    repo: JobRepo = _repo()
+    job = await repo.create(PROJECT, KIND)  # queued（非 awaiting）
+    assert await repo.claim_awaiting_to_running(job.id) is None
+
+
+async def test_claim_absent_job_returns_none() -> None:
+    repo: JobRepo = _repo()
+    assert await repo.claim_awaiting_to_running(uuid.uuid4()) is None
+
+
 # ---- progress (clamped) ----