feat(web): Scope B B1 — 多章工作流链前端 UI（发起/轮询/裁决续跑）

链页 app/projects/[id]/chains（RSC fetchProject）+ ChainPage/ChainStarter/
ChainProgress/ChainAdjudication；lib/chain 纯函数（result 收窄/相位映射/resume 组装）。
复用 useJobPoll 轮询、ConflictCard + decisions.ts 裁决、normalizeConflicts/latestReview、
friendlyError；nav 加 chains 入口。awaiting（interrupt）→ 读该章冲突渲 ConflictCard →
POST .../chains/runs/{job_id}/resume 续跑。gen:api 纳入 chains run/resume。
守 #5（链暂停=等裁决，token/正文不入 job result）。

apps/web/lib/chain/chain.test.ts

@@ -0,0 +1,112 @@
+import { describe, expect, it } from "vitest";
+
+import { emptyDecisions, setNote, setVerdict } from "@/lib/review/decisions";
+import type { JobView } from "@/lib/jobs/job";
+import {
+  buildResumeRequest,
+  chainPhase,
+  chainResultView,
+} from "./chain";
+
+function job(result: Record<string, unknown> | null): JobView {
+  return {
+    id: "j1",
+    kind: "chain",
+    status: "running",
+    progress: 0,
+    result,
+    error: null,
+  };
+}
+
+describe("chainResultView", () => {
+  it("narrows a completed chain result", () => {
+    const view = chainResultView(
+      job({
+        chain_key: "draft_volume",
+        written: [1, 2, 3],
+        completed: true,
+        awaiting_chapter: null,
+      }),
+    );
+    expect(view).toEqual({
+      chainKey: "draft_volume",
+      written: [1, 2, 3],
+      awaitingChapter: null,
+      completed: true,
+    });
+  });
+
+  it("narrows an awaiting result (interrupt on a chapter)", () => {
+    const view = chainResultView(
+      job({
+        chain_key: "draft_volume",
+        written: [1],
+        completed: false,
+        awaiting_chapter: 2,
+      }),
+    );
+    expect(view.awaitingChapter).toBe(2);
+    expect(view.completed).toBe(false);
+    expect(view.written).toEqual([1]);
+  });
+
+  it("returns safe defaults for null/garbage result", () => {
+    expect(chainResultView(job(null))).toEqual({
+      chainKey: null,
+      written: [],
+      awaitingChapter: null,
+      completed: false,
+    });
+    expect(
+      chainResultView(job({ written: "nope", awaiting_chapter: "x" })).written,
+    ).toEqual([]);
+  });
+
+  it("keeps only finite integer chapter numbers in written", () => {
+    const view = chainResultView(
+      job({ written: [1, "2", 3.5, null, 4] }),
+    );
+    expect(view.written).toEqual([1, 4]);
+  });
+});
+
+describe("chainPhase", () => {
+  it("maps polling with no awaiting chapter to running", () => {
+    expect(chainPhase("polling", null)).toBe("running");
+  });
+
+  it("maps any awaiting chapter to awaiting (interrupt signal is authoritative)", () => {
+    // 后端 interrupt 时置 status=awaiting_input（被 narrowJob 抹平成 queued→仍 polling），
+    // 但 result.awaiting_chapter 已置数；运行中该值恒 null，故它是暂停的权威信号。
+    expect(chainPhase("polling", 2)).toBe("awaiting");
+    expect(chainPhase("done", 2)).toBe("awaiting");
+  });
+
+  it("maps done + no awaiting to completed", () => {
+    expect(chainPhase("done", null)).toBe("completed");
+  });
+
+  it("maps error to failed (even if an awaiting chapter lingers)", () => {
+    expect(chainPhase("error", null)).toBe("failed");
+    expect(chainPhase("error", 2)).toBe("failed");
+  });
+});
+
+describe("buildResumeRequest", () => {
+  it("includes only resolved decisions and trims notes (reuses accept decision logic)", () => {
+    let drafts = emptyDecisions(3);
+    drafts = setVerdict(drafts, 0, "accept");
+    drafts = setVerdict(drafts, 2, "manual");
+    drafts = setNote(drafts, 2, "  改成后天淬炼  ");
+    const req = buildResumeRequest(drafts);
+    expect(req.decisions).toEqual([
+      { conflict_index: 0, verdict: "accept" },
+      { conflict_index: 2, verdict: "manual", note: "改成后天淬炼" },
+    ]);
+  });
+
+  it("empty drafts → empty decisions list", () => {
+    expect(buildResumeRequest([])).toEqual({ decisions: [] });
+  });
+});

apps/web/lib/chain/chain.ts

@@ -0,0 +1,67 @@
+// 多章工作流链前端纯逻辑（Scope B）：把 `GET /jobs/{id}` 的链 job result 安全收窄成
+// 视图模型；把轮询状态 + interrupt 标志映射成链相位；裁决草稿 → resume 请求体。
+// 纯逻辑（无 React / 无 fetch），便于 node 环境单测。链走 job 轮询（非 SSE）。
+
+import type { ChainResumeRequest } from "@/lib/api/types";
+import type { JobView, PollStatus } from "@/lib/jobs/job";
+import { buildAcceptRequest, type DecisionDraft } from "@/lib/review/decisions";
+
+// 链 job result 的视图模型（与后端 `_chain_result` 字段对齐：chain_key/written/completed/
+// awaiting_chapter）。token/正文绝不入 result（不变量 #5 / chain §5），故此处只有进度元数据。
+export interface ChainResultView {
+  chainKey: string | null;
+  // 已写完（已验收/已晋升）的章号清单。
+  written: number[];
+  // interrupt 命中、等作者裁决的章号；null = 未暂停（跑完或运行中）。
+  awaitingChapter: number | null;
+  // 全链跑完（无 interrupt 残留）。
+  completed: boolean;
+}
+
+function asIntList(v: unknown): number[] {
+  if (!Array.isArray(v)) return [];
+  return v.filter(
+    (n): n is number => typeof n === "number" && Number.isInteger(n),
+  );
+}
+
+function asIntOrNull(v: unknown): number | null {
+  return typeof v === "number" && Number.isInteger(v) ? v : null;
+}
+
+// 把链 job 的 result 收窄成 ChainResultView（缺字段/脏数据给安全默认，守边界 #not-trust）。
+export function chainResultView(job: JobView): ChainResultView {
+  const r = job.result ?? {};
+  return {
+    chainKey: typeof r["chain_key"] === "string" ? r["chain_key"] : null,
+    written: asIntList(r["written"]),
+    awaitingChapter: asIntOrNull(r["awaiting_chapter"]),
+    completed: r["completed"] === true,
+  };
+}
+
+// 链相位（驱动页面 UI 分支）：运行中 / 待裁决 / 跑完 / 失败。
+export type ChainPhase = "running" | "awaiting" | "completed" | "failed";
+
+// 后端 interrupt 时把 job 置 awaiting_input（非 done/failed）+ result.awaiting_chapter=N——
+// `narrowJob` 把未知态 awaiting_input 归到 "queued"，故轮询 reducer 仍 polling；运行中
+// awaiting_chapter 恒为 null，仅 interrupt 命中才置数，故以 `awaitingChapter !== null` 为
+// 暂停的权威信号（不依赖被抹平的原始状态），让页面在暂停时进入裁决相而非空轮询（不变量 #5）。
+export function chainPhase(
+  pollStatus: PollStatus,
+  awaitingChapter: number | null,
+): ChainPhase {
+  if (pollStatus === "error") return "failed";
+  if (awaitingChapter !== null) return "awaiting";
+  if (pollStatus === "done") return "completed";
+  return "running";
+}
+
+// 裁决草稿 → resume 请求体。复用 accept 的裁决组装逻辑（DRY；resume.decisions 与
+// accept.decisions 同为 ConflictDecision[]），仅丢弃 final_text（链续跑不带终稿）。
+export function buildResumeRequest(
+  drafts: readonly DecisionDraft[],
+): ChainResumeRequest {
+  const { decisions } = buildAcceptRequest("", drafts);
+  return { decisions };
+}