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/components/chain/ChainPage.tsx

@@ -0,0 +1,119 @@
+"use client";
+
+import { useCallback, useEffect, useMemo, useState } from "react";
+
+import { AppShell } from "@/components/AppShell";
+import { useToast } from "@/components/Toast";
+import { api } from "@/lib/api/client";
+import { chainPhase, chainResultView } from "@/lib/chain/chain";
+import { friendlyError } from "@/lib/errors/messages";
+import { useJobPoll } from "@/lib/jobs/useJobPoll";
+import type { ProjectResponse } from "@/lib/api/types";
+import { ChainAdjudication } from "./ChainAdjudication";
+import { ChainProgress } from "./ChainProgress";
+import { ChainStarter } from "./ChainStarter";
+
+interface ChainPageProps {
+  project: ProjectResponse;
+}
+
+const CHAIN_KEY = "draft_volume";
+
+// 多章工作流链页（Scope B B1）：发起链(POST run)→job 轮询进度→interrupt 命中则读该章冲突裁决→
+// POST resume 续跑。复用 useJobPoll（轮询）+ ConflictCard/decisions（裁决）+ friendlyError（文案）。
+// 链是后台任务，走 job 轮询而非 SSE。awaiting 时停轮询（后端把 job 置 awaiting_input，
+// narrowJob 抹平成 queued 会无限轮询）→ 裁决面板 resume 后再重启轮询同一 job。
+export function ChainPage({ project }: ChainPageProps) {
+  const poll = useJobPoll();
+  const toast = useToast();
+  const [jobId, setJobId] = useState<string | null>(null);
+  const [starting, setStarting] = useState(false);
+
+  const job = poll.job;
+  const result = useMemo(
+    () => (job ? chainResultView(job) : null),
+    [job],
+  );
+  const awaitingChapter = result?.awaitingChapter ?? null;
+  const phase = chainPhase(poll.status, awaitingChapter);
+
+  // awaiting 命中：停轮询（后端 job=awaiting_input 被 narrowJob 抹成 queued 会空转）。
+  useEffect(() => {
+    if (phase === "awaiting") poll.reset();
+  }, [phase, poll]);
+
+  const onStart = useCallback(
+    async (startChapterNo: number, count: number): Promise<void> => {
+      setStarting(true);
+      try {
+        const { data, error } = await api.POST(
+          "/projects/{project_id}/chains/{chain_key}/run",
+          {
+            params: {
+              path: { project_id: project.id, chain_key: CHAIN_KEY },
+            },
+            body: { start_chapter_no: startChapterNo, count },
+          },
+        );
+        if (error || !data) {
+          toast(friendlyError(undefined).text, "error");
+          return;
+        }
+        setJobId(data.job_id);
+        poll.poll(data.job_id);
+      } catch {
+        toast("发起链请求异常，请检查网络。", "error");
+      } finally {
+        setStarting(false);
+      }
+    },
+    [project.id, poll, toast],
+  );
+
+  // 续跑成功：重启轮询同一 job（resume 已 202，图从检查点续）。
+  const onResumed = useCallback((): void => {
+    if (jobId) poll.poll(jobId);
+  }, [jobId, poll]);
+
+  const showProgress = jobId !== null && result !== null;
+  // 链运行中/等待裁决时禁止重复发起。
+  const busy = starting || (jobId !== null && phase === "running");
+
+  return (
+    <AppShell
+      title={project.title}
+      subtitle="多章工作流链"
+      projectId={project.id}
+      activeNav="chains"
+    >
+      <div className="mx-auto flex w-full max-w-3xl flex-col gap-6 p-6">
+        <ChainStarter onStart={(s, c) => void onStart(s, c)} disabled={busy} />
+
+        {showProgress && result ? (
+          <ChainProgress phase={phase} progress={poll.progress} result={result} />
+        ) : null}
+
+        {phase === "awaiting" &&
+        awaitingChapter !== null &&
+        jobId !== null ? (
+          <ChainAdjudication
+            projectId={project.id}
+            jobId={jobId}
+            chapterNo={awaitingChapter}
+            onResumed={onResumed}
+          />
+        ) : null}
+
+        {phase === "failed" ? (
+          <p className="text-sm text-conflict">
+            {poll.error ?? "链运行失败，请重试。"}
+          </p>
+        ) : null}
+
+        {phase === "completed" ? (
+          <p className="text-sm text-pass">本链已全部跑完。</p>
+        ) : null}
+      </div>
+    </AppShell>
+  );
+}