feat: M3 — 伏笔账本 + 节奏引擎 + 大纲（含并发记账 bugfix）

- 伏笔账本：纯函数状态机(OPEN/PARTIAL/CLOSED/OVERDUE) + ForeshadowLedger repo；验收后到期扫描(BackgroundTask 自建 session 置 OVERDUE)；登记/状态变更端点
- 节奏 + 三审齐：foreshadow-analyst + pace-checker 并入 LangGraph 并行审(REVIEW_SPECS)，collect 分列落 chapter_reviews(conflicts/foreshadow_sug/pace)，review SSE 加 foreshadow/pace 事件
- 大纲：outliner Agent 产 OutlineResult(含 foreshadow_windows)，POST /outline 逐章 upsert outline 表；GET /foreshadow?status= 看板
- 前端：伏笔四泳道看板(OVERDUE 琥珀) + 大纲编辑器(窗口徽标) + 节奏节拍图(▁▃▅) + 审稿页消费 foreshadow/pace SSE
- bugfix(T3.8)：并行三审共用请求 session 记账触发 'Session is already flushing' → foreshadow/pace 静默丢失；SqlAlchemyLedgerSink.record 改 add-only(靠端点/事务 commit)，加并发回归测试
- M3 E2E：真实 DB + mock 网关零 token 走通 埋设→进展→验收后扫描 OVERDUE→看板 + 大纲含窗口 + 三审齐 SSE/留痕；E2E 暴露并钉住上述 bug
- 门禁绿：mypy 111 / pytest 228(0 xfailed) / alembic 无漂移；前端 gen:api/lint/tsc/vitest 69/build

apps/api/tests/test_review_accept.py

@@ -17,6 +17,7 @@ from fakes_projects import (
     FakeReviewGateway,
     FakeReviewRepo,
     FakeSession,
+    FakeSessionFactory,
 )
 from test_projects import _empty_memory_repos
 from ww_agents import ContinuityReview
@@ -50,6 +51,7 @@ def _make_client(
         get_memory_repos,
         get_review_gateway,
         get_review_repo,
+        get_session_factory,
     )
     from ww_db import get_session
 
@@ -68,6 +70,7 @@ def _make_client(
     app.dependency_overrides[get_review_gateway] = lambda: review_gateway
     app.dependency_overrides[get_digest_gateway] = lambda: digest_gateway
     app.dependency_overrides[get_session] = lambda: session
+    app.dependency_overrides[get_session_factory] = lambda: FakeSessionFactory()
     transport = httpx.ASGITransport(app=app)
     client = httpx.AsyncClient(transport=transport, base_url="http://test")
     return client, chapter_repo, review_repo, digest_repo, session