Error: Failed to execute ip netns add

I'm running in a Docker container, which does not (cannot) have `ip` installed.

```bash
user@test-workspace-88b1c24e:/workspace/test-workspace$ sudo ~user/.cargo/bin/httpjail --js "r.host === 'github.com'" -- hello
21:58:40.666 ERROR httpjail::sys_resource: Failed to cleanup resource on drop: Failed to execute ip netns del
Error: Failed to execute ip netns add

Caused by:
No such file or directory (os error 2)
```

I don't think this can ever work within a Docker container.

在没有 `ip` 的 Docker 容器中重现 `httpjail --js ... -- hello` 命令，然后检查通过该入口点到达的网络命名空间设置。确认此环境是否受支持，并确定所需命令不可用时的预期行为。

由索引模型根据 Issue 内容生成。