Function GetTreeViewChildren 

pub async fn GetTreeViewChildren(
    ApplicationHandle: AppHandle<Wry>,
    _State: State<'_, Arc<ApplicationState>>,
    ViewId: String,
    ElementHandle: Option<String>,
) -> Result<Value, String>

A specific Tauri command handler for the UI to fetch the children of a tree view node. This handler dispatches to the correct provider (native or proxied).