refactor(tasks): 后台任务改读宿主客户端 jobs 服务，删除自建三条路由

- 新增 src/client/jobs-client.ts：结构探测 ctx.jobs（watchRows / observe /
  state / kill），引用计数的按会话 roster 订阅、只观测展开的那一行、
  跨树去重（无主任务归到承载它的被观测会话，树外 owner 丢弃）。
- 抽屉与输出浮窗改读该服务：行来自推送 roster（状态 / 时长 / owner / 进度），
  输出面换 TerminalBlock 显示宿主为观察者流的保留输出（gapBefore → 截断提示、
  error → 失败提示），kill 走 jobs.kill(owner, jobId)，两击确认不变。
- 自动激活（use-host-feeds）改骑同一条推送 roster；detectNewJob 增加
  「观测起点时钟」参数，避免「页面打开时已在跑的任务」被当成新工作。
- 删除 src/jobs-routes.ts（+ tests/jobs-routes.spec.ts）、index.ts 的三条路由、
  api.jobsList/jobOutput/jobKill 与 JobOutputResult、context-types 的
  SidebarJobsService（换成 SidebarClientJobsService/SidebarJobsSnapshot/
  SidebarObservedJob 镜像，SidebarJobView 补 owner/progress）、
  页面里的 jobs.list 轮询与 collectTreeJobs。
- 三个 spec 改用假 ctx.jobs 服务（jobs-view 14 例 / 自动激活 12 例 /
  页面 20 例）：观测只在展开行、切换与关闭释放观测、watch 隐藏时不建立、
  卸载时全部释放、无服务时不渲染任务面。

验证：typecheck / lint 通过；pnpm test 1240 passed / 9 skipped；pnpm build + pack 通过。

(cherry picked from commit 7d9b82e73190218f05910433ed520cb90e4d4ab2)

src/client/block-labels.ts

@@ -0,0 +1,69 @@
+/**
+ * Display copy for the host primitives the sidebar renders OUTSIDE the main
+ * conversation: `TerminalBlock` (a captured command's output surface) is
+ * cordis-free and takes every label as a prop, so the owning render site must
+ * supply them.
+ *
+ * One builder, two consumers (the Side Chat tool card and the Tasks page's
+ * background-job output panel): the two surfaces must read identically, and a
+ * new required label on the host side has exactly one place to land.
+ */
+import { t } from './locales.ts'
+
+/** Labels for the sidebar's markdown / diff / read Block chrome. */
+export interface BlockLabels {
+  copy: string
+  copied: string
+  collapse: string
+  collapseAria: string
+  expand: (hidden: number) => string
+  expandAria: (hidden: number) => string
+}
+
+/**
+ * The sidebar's Blocks reuse the Side Chat dictionary's chrome family (copy
+ * pair + the collapse/expand family that is common to every Block kind).
+ */
+export function blockLabels(): BlockLabels {
+  return {
+    copy: t('copy'),
+    copied: t('copied'),
+    collapse: t('sideChatBlockCollapse'),
+    collapseAria: t('sideChatBlockCollapseAria'),
+    expand: (hidden: number) => t('sideChatBlockExpand', { hidden }),
+    expandAria: (hidden: number) => t('sideChatBlockExpandAria', { hidden }),
+  }
+}
+
+/** The `TerminalBlockLabels` shape (structural mirror; the host owns the type). */
+export interface TerminalLabels {
+  signal: (signal: string) => string
+  exitCode: (exitCode: number) => string
+  noExitCode: string
+  running: string
+  failed: string
+  done: string
+  copy: string
+  copied: string
+  noOutput: string
+  collapseAria: string
+  collapse: string
+  expandAria: (hidden: number) => string
+  expand: (hidden: number) => string
+}
+
+/** Labels for one `TerminalBlock` (a captured command plus its output). */
+export function terminalBlockLabels(): TerminalLabels {
+  return {
+    ...blockLabels(),
+    signal: (signal: string) => t('sideChatBlockSignal', { signal }),
+    exitCode: (exitCode: number) => t('sideChatBlockExitCode', { code: exitCode }),
+    // DSH 0.1.6-alpha.2 added this pill text: a settle the view cannot
+    // name (killed by an unknown signal, or never started).
+    noExitCode: t('sideChatBlockNoExitCode'),
+    running: t('sideChatBlockRunning'),
+    failed: t('sideChatBlockFailed'),
+    done: t('sideChatBlockDone'),
+    noOutput: t('sideChatBlockNoOutput'),
+  }
+}