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/web/app/projects/[id]/foreshadow/page.tsx

@@ -0,0 +1,23 @@
+import { notFound } from "next/navigation";
+
+import { ForeshadowBoard } from "@/components/foreshadow/ForeshadowBoard";
+import { fetchForeshadow, fetchProject } from "@/lib/api/server";
+
+interface PageProps {
+  params: Promise<{ id: string }>;
+}
+
+// 伏笔看板页（UX §6.8）。Server Component 取项目 + 全量伏笔（GET .../foreshadow）；
+// ForeshadowBoard（Client）按 status 分四泳道并承载登记/状态变更交互。
+export default async function ForeshadowPage({ params }: PageProps) {
+  const { id } = await params;
+  try {
+    const project = await fetchProject(id);
+    const board = await fetchForeshadow(id);
+    return (
+      <ForeshadowBoard project={project} initialItems={board.foreshadow ?? []} />
+    );
+  } catch {
+    notFound();
+  }
+}

apps/web/app/projects/[id]/outline/page.tsx

@@ -0,0 +1,20 @@
+import { notFound } from "next/navigation";
+
+import { OutlineEditor } from "@/components/outline/OutlineEditor";
+import { fetchProject } from "@/lib/api/server";
+
+interface PageProps {
+  params: Promise<{ id: string }>;
+}
+
+// 大纲编辑器页（UX §6.7）。Server Component 取项目；OutlineEditor（Client）按需
+// 触发 POST .../outline 生成大纲（M3 无 GET 大纲端点，进页空、生成后填充）。
+export default async function OutlinePage({ params }: PageProps) {
+  const { id } = await params;
+  try {
+    const project = await fetchProject(id);
+    return <OutlineEditor project={project} initialChapters={[]} />;
+  } catch {
+    notFound();
+  }
+}