feat: integrate 5 feature branches + daemon/job 命令层级化 + 跨平台后台引擎 + TypeScript 错误修复

Squashed merge of:
1. fix/mcp-tsc-errors — 修复上游 MCP 重构后的 tsc 错误和测试失败
2. feat/pipe-mute-disconnect — Pipe IPC 逻辑断开、/lang 命令、mute 状态机
3. feat/stub-recovery-all — 实现全部 stub 恢复 (task 001-012)
4. feat/kairos-activation — KAIROS 激活解除阻塞 + 工具实现
5. codex/openclaw-autonomy-pr — 自治权限系统、运行记录、managed flows

Additional:
6. daemon/job 命令层级化重构 (subcommand 架构)
7. 跨平台后台引擎抽象 (detached/tmux engines)
8. 修复 src/ 中 43 个预存在的 TypeScript 类型错误
9. 修复 langfuse isolated test mock 完整性
10. 修复 CodeRabbit 审查的 Critical/Major/Minor 问题
11. remote-control-server logger 抽象 (测试 stderr 静默化)
12. /simplify 审查修复 (代码复用、质量、效率)

src/cli/bg/engines/index.ts

@@ -0,0 +1,17 @@
+export type { BgEngine, BgStartOptions, BgStartResult, SessionEntry } from '../engine.js'
+
+export async function selectEngine(): Promise<import('../engine.js').BgEngine> {
+  if (process.platform === 'win32') {
+    const { DetachedEngine } = await import('./detached.js')
+    return new DetachedEngine()
+  }
+
+  const { TmuxEngine } = await import('./tmux.js')
+  const tmux = new TmuxEngine()
+  if (await tmux.available()) {
+    return tmux
+  }
+
+  const { DetachedEngine } = await import('./detached.js')
+  return new DetachedEngine()
+}