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/lib/review/sse.ts

@@ -19,6 +19,29 @@ export interface ReviewConflict {
 
 export type SectionStatus = "started" | "done" | "incomplete";
 
+// 伏笔建议（C4 扩 T3.3）：planted=新埋待确认 / resolved=疑似回收（只读建议）。
+export type ForeshadowKind = "planted" | "resolved";
+
+export interface ForeshadowSuggestion {
+  kind: ForeshadowKind;
+  code?: string | null;
+  title: string;
+  where?: string | null;
+  note?: string | null;
+}
+
+// 节奏报告（C4 扩 T3.3）：注水段 + 章末钩子 + 爽点节拍图。
+export interface PaceIssue {
+  where: string;
+  reason: string;
+}
+
+export interface PaceReport {
+  water: PaceIssue[];
+  hook: boolean;
+  beat_map: number[];
+}
+
 export interface SectionEvent {
   event: "section";
   data: { name: string; status: SectionStatus };
@@ -27,6 +50,24 @@ export interface ConflictEvent {
   event: "conflict";
   data: ReviewConflict;
 }
+export interface ForeshadowEvent {
+  event: "foreshadow";
+  data: {
+    kind: ForeshadowKind;
+    code?: string | null;
+    title: string;
+    where?: string | null;
+    note?: string | null;
+  };
+}
+export interface PaceEvent {
+  event: "pace";
+  data: {
+    water: PaceIssue[];
+    hook: boolean;
+    beat_map: number[];
+  };
+}
 export interface DoneEvent {
   event: "done";
   data: { length: number };
@@ -38,10 +79,19 @@ export interface ErrorEvent {
 export type ReviewSseEvent =
   | SectionEvent
   | ConflictEvent
+  | ForeshadowEvent
+  | PaceEvent
   | DoneEvent
   | ErrorEvent;
 
-const KNOWN_EVENTS = new Set(["section", "conflict", "done", "error"]);
+const KNOWN_EVENTS = new Set([
+  "section",
+  "conflict",
+  "foreshadow",
+  "pace",
+  "done",
+  "error",
+]);
 
 // 把一个完整 SSE 块（多行）解析成事件；无法解析则返回 null（跳过）。
 export function parseReviewBlock(block: string): ReviewSseEvent | null {
@@ -108,6 +158,8 @@ export interface ReviewStreamState {
   phase: ReviewPhase;
   sections: ReviewSection[];
   conflicts: ReviewConflict[];
+  foreshadow: ForeshadowSuggestion[];
+  pace: PaceReport | null;
   error: { code: string; message: string; request_id?: string | null } | null;
 }
 
@@ -115,6 +167,8 @@ export const initialReviewState: ReviewStreamState = {
   phase: "idle",
   sections: [],
   conflicts: [],
+  foreshadow: [],
+  pace: null,
   error: null,
 };
 
@@ -136,6 +190,18 @@ export function reduceReview(
         phase: "reviewing",
         conflicts: [...state.conflicts, event.data],
       };
+    case "foreshadow":
+      return {
+        ...state,
+        phase: "reviewing",
+        foreshadow: [...state.foreshadow, { ...event.data }],
+      };
+    case "pace":
+      return {
+        ...state,
+        phase: "reviewing",
+        pace: { ...event.data },
+      };
     case "done":
       return { ...state, phase: "done" };
     case "error":