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/index.ts

@@ -41,7 +41,6 @@ import { launchExternal } from './open-external.ts'
 import * as git from './git.ts'
 import { SettingsConflictError } from '@deepseek-ai/dsh-settings'
 import { AgentOpenRegistry, registerOpenTool, type AgentOpenRequest } from './agent-opens.ts'
-import { buildJobsApi, type SidebarJobsRoutes } from './jobs-routes.ts'
 import { buildSubagentLiveApi, type SidebarSubagentLiveRoutes } from './subagent-live-route.ts'
 import { buildTeamsApi, type SidebarTeamsRoutes } from './team-routes.ts'
 import { buildWorkflowsApi, type SidebarWorkflowRoutes } from './workflow-routes.ts'
@@ -264,12 +263,6 @@ function buildApi(
     const requested = typeof record?.worktree === 'string' && record.worktree !== '' ? record.worktree : undefined
     return { sessionId: base.sessionId, cwd: await git.resolveWorktree(base.cwd, requested) }
   }
-  // Background jobs: the LIST rides the harness's `session/jobs` push
-  // mirror, so these routes only replay output the model has read (from the
-  // session's own event log — no DSH source is touched, the model's
-  // job_output cursor is never consumed) and kill (the registry's stock
-  // API). A deployment without the jobs registry downgrades kill to a 503.
-  const jobsApi: SidebarJobsRoutes = buildJobsApi(ctx, resolved.readLimit)
   // Subagent live previews: one batch request instead of N per-child
   // `subagents.history` calls. The route degrades to a 503 when the host
   // subagent runtime is absent (the page has no topology to show anyway).
@@ -484,16 +477,6 @@ function buildApi(
       const window = filtered.length > CHANGES_EVENTS_CAP ? filtered.slice(filtered.length - CHANGES_EVENTS_CAP) : filtered
       return { events: window, lastSeq: window.at(-1)?.seq ?? afterSeq }
     },
-    // Background jobs: list the caller's own jobs, read one job's output (a
-    // REPLAY of what the model has read so far, from the owner session's
-    // event log — the model's job_output cursor is never touched, so the
-    // human pane can never steal the agent's bytes), and kill one job. The
-    // list route exists because DSH 0.1.7 deleted the session/jobs push
-    // mirror the Tasks page used to read. Kill is fenced to the owning
-    // session by the jobs registry.
-    'jobs.list': (payload) => jobsApi.list(payload),
-    'jobs.output': (payload) => jobsApi.output(payload),
-    'jobs.kill': (payload) => jobsApi.kill(payload),
     // Subagent live previews: one batch request per refresh; the route folds
     // the newest text/tool activity of every running child in the tree.
     'subagents.live': (payload) => subagentLiveApi.live(payload),