pub fn tab(title: &str, system_image: &str, content: &ViewHandle) -> ViewHandleExpand description
Tab("Home", systemImage: "house") { … } — one tab of a modern TabView.
The older way to build a tab is .tabItem { Label(…) } on the page itself,
which is what tab_item binds. Tab is the replacement:
the tab and its label are one value rather than a modifier on the content,
which is what lets a TabView know its tabs without rendering them.
Tab is not a View — it is a TabContent, and only a TabView accepts
one.