Show action buttons in export previews

QLPreviewController only renders its share, print and open-in actions
when it is inside a navigation controller, so diagram and report
previews were dead ends. Wrap it in one, add an explicit Done button
and assert both in a UI test.

Cable/Loads/LoadsView.swift

@@ -232,8 +232,10 @@ struct LoadsView: View {
             )
         ) {
             if let previewURL {
-                QuickLookPreview(url: previewURL)
-                    .ignoresSafeArea()
+                QuickLookPreview(url: previewURL) {
+                    self.previewURL = nil
+                }
+                .ignoresSafeArea()
             }
         }
         .onChange(of: previewURL) { _, newValue in

Cable/Loads/QuickLookPreview.swift

@@ -5,38 +5,53 @@
 
 import QuickLook
 import SwiftUI
+import UIKit
 
 /// Presents a single exported file (PDF or PNG) in Quick Look so the user can
 /// inspect it before sharing.
 ///
 /// SwiftUI's `quickLookPreview(_:)` modifier is macOS-only, so iOS wraps
-/// `QLPreviewController` directly.
+/// `QLPreviewController` directly. The controller only shows its action
+/// buttons — share, print, open in another app — when it sits inside a
+/// navigation controller, so it is wrapped in one and gets an explicit Done
+/// button to close the sheet.
 struct QuickLookPreview: UIViewControllerRepresentable {
     let url: URL
+    var onDone: () -> Void
 
-    func makeUIViewController(context: Context) -> QLPreviewController {
-        let controller = QLPreviewController()
-        controller.dataSource = context.coordinator
-        return controller
+    func makeUIViewController(context: Context) -> UINavigationController {
+        let preview = QLPreviewController()
+        preview.dataSource = context.coordinator
+        preview.navigationItem.leftBarButtonItem = UIBarButtonItem(
+            barButtonSystemItem: .done,
+            target: context.coordinator,
+            action: #selector(Coordinator.done)
+        )
+        preview.navigationItem.leftBarButtonItem?.accessibilityIdentifier = "quick-look-done-button"
+        return UINavigationController(rootViewController: preview)
     }
 
-    func updateUIViewController(_ controller: QLPreviewController, context: Context) {
+    func updateUIViewController(_ controller: UINavigationController, context: Context) {
+        context.coordinator.onDone = onDone
+
         guard context.coordinator.url != url as NSURL else { return }
         context.coordinator.url = url as NSURL
-        controller.reloadData()
+        (controller.viewControllers.first as? QLPreviewController)?.reloadData()
     }
 
     func makeCoordinator() -> Coordinator {
-        Coordinator(url: url as NSURL)
+        Coordinator(url: url as NSURL, onDone: onDone)
     }
 
     // MARK: - Coordinator
 
     final class Coordinator: NSObject, QLPreviewControllerDataSource {
         var url: NSURL
+        var onDone: () -> Void
 
-        init(url: NSURL) {
+        init(url: NSURL, onDone: @escaping () -> Void) {
             self.url = url
+            self.onDone = onDone
         }
 
         func numberOfPreviewItems(in controller: QLPreviewController) -> Int { 1 }
@@ -44,5 +59,9 @@ struct QuickLookPreview: UIViewControllerRepresentable {
         func previewController(_ controller: QLPreviewController, previewItemAt index: Int) -> QLPreviewItem {
             url
         }
+
+        @objc func done() {
+            onDone()
+        }
     }
 }