Fix A11y tests (#5104)

* replace NavigationStack with ElementNavigationStack to allow the content to be rendered without a NavigationStack in a11y tests

* fix a11y tests

* update xcodeproject

* swiftformat fix

* use iOS 26.1 for CI

* use a wrapper to solve the issue for a11y tests

* ElementNavigationStack only uses the trick in DEBUG mode, and added a swiftlint rule to prevent the usage of NavigationStack

ElementX/Sources/AccessibilityTests/AccessibilityTestsAppCoordinator.swift

@@ -104,11 +104,8 @@ struct PreviewsWrapperView: View {
     @Environment(\.dynamicTypeSize) var dynamicTypeSize
     
     var body: some View {
-        if wrapper.currentIndex < 0 || wrapper.isDone {
-            EmptyView()
-        } else {
+        if wrapper.currentIndex >= 0, !wrapper.isDone {
             wrapper.currentPreview.content
-                // This ID raises UIKit assertions on iOS 26 but is needed otherwise toolbars go missing and some timeline items won't resize.
                 .id("\(wrapper.previewName)-\(dynamicTypeSize)")
         }
     }