chore: v0.8.0 — 任务管理页（子代理拓扑 + 后台命令底部输出 Dock、两击确认终止）

- tab 更名为任务管理：同页显示当前树全部后台命令（bash/pwsh 徽标、状态、时长、属主、退出码）
- 点击任务行在侧边栏底部共享 Dock 显示输出（sticky 终端式、自动跟随、单一轮询实例）
- 运行中任务两击确认强制终止；大量任务时列表保持紧凑、排序变动不跳动
- 新增 /sidebar/api tasks.output（非消费 peek，不偷模型 task_output 字节）与 tasks.kill 路由
- 修复任务镜像清空时的 React #300 hook 顺序崩溃（useCallback 移到提前 return 之前）+ 回归测试

src/client/api.ts

@@ -8,6 +8,7 @@
  */
 import { encodeHtmlUrl } from '../html-route.ts'
 import type { BrowserProbeResult } from './browser.ts'
+import type { SidebarTaskStatus } from '../context-types.ts'
 
 /** One wire failure. */
 export class SidebarApiError extends Error {
@@ -60,6 +61,15 @@ export interface FsTextResult { kind: 'text'; content: string; truncated: boolea
  *  `head` carries the first bytes (base64) for viewer detect sniffing. */
 export interface FsBinaryResult { kind: 'binary'; size: number; truncated: boolean; head: string }
 
+/** One tasks.output response: the peeked full text (capped) plus the wire status. */
+export interface TaskOutputResult {
+  text: string
+  /** True when the host capped the text at its output limit. */
+  truncated: boolean
+  status: SidebarTaskStatus
+  detail?: string
+}
+
 async function call<T>(method: string, payload: Record<string, unknown>, signal?: AbortSignal): Promise<T> {
   let response: Response
   try {
@@ -145,6 +155,20 @@ export const api = {
   /** Release an agent terminal by uuid (tab closed while WS was down). */
   agentPtyClose: (uuid: string) =>
     call<{ ok: true }>('agent-pty.close', { uuid }),
+  /**
+   * Full accumulated output of one background task (the host's NON-CONSUMING
+   * peek — the model's task_output cursor and report bit are untouched, so a
+   * human watching a stream never steals the agent's bytes). The scope MUST
+   * be the task's OWNER session (the tasks registry fences by session id).
+   */
+  taskOutput: (scope: SessionScope, id: string, signal?: AbortSignal) =>
+    call<TaskOutputResult>('tasks.output', scopePayload(scope, { id }), signal),
+  /** Request cancellation of one background task (live tasks flip to stopping). */
+  taskKill: (scope: SessionScope, id: string, reason?: string) =>
+    call<{ ok: true; outcome: 'requested' | 'already-finished' }>('tasks.kill', scopePayload(scope, {
+      id,
+      ...(reason !== undefined ? { reason } : {}),
+    })),
   /** Read the side card preferences (plugin-global, no session scope). */
   settingsGet: () =>
     call<{ value?: unknown; revision?: number }>('settings.get', {}),