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/nav/items.ts

@@ -10,7 +10,8 @@ export type ActiveNav =
   | "codex"
   | "rules"
   | "skills"
-  | "toolbox";
+  | "toolbox"
+  | "chains";
 
 export interface NavItem {
   href: string;
@@ -35,6 +36,7 @@ export function projectNavItems(projectId: string): NavItem[] {
       key: "foreshadow",
     },
     { href: `/projects/${projectId}/review`, label: "审稿", key: "review" },
+    { href: `/projects/${projectId}/chains`, label: "多章链", key: "chains" },
     { href: `/projects/${projectId}/style`, label: "文风", key: "style" },
     { href: `/projects/${projectId}/codex`, label: "设定库", key: "codex" },
     { href: `/projects/${projectId}/toolbox`, label: "工具箱", key: "toolbox" },