#5 fix camera capture preview after shooting

- Dismiss the camera fullScreenCover through the SwiftUI binding
  synchronously in the picker delegate before background file
  preparation, so UIImagePickerController no longer dismisses itself
  and desynchronizes the presentation state that the preview sheet
  waits on.
- Keep the archive-sync suspension reserved across the dismissal and
  surface an explicit error when the captured file fails to prepare.
- Add verify.sh invariants for the camera dismissal flow.

Sources/Shared/UI/SystemPhotoCameraView.swift

@@ -12,6 +12,13 @@ import UIKit
 
 @MainActor
 struct SystemPhotoCameraView: UIViewControllerRepresentable {
+    /// Called synchronously on the main thread inside
+    /// `didFinishPickingMediaWithInfo`, before any background preparation.
+    /// The host must flip its `isPresented` binding here so SwiftUI drives
+    /// the dismissal; letting UIImagePickerController dismiss itself leaves
+    /// the fullScreenCover state desynchronized and breaks the follow-up
+    /// preview presentation.
+    let onDismissRequest: () -> Void
     let onMedia: (Result<CapturedCameraMedia, Error>) -> Void
     let onCancel: () -> Void
 
@@ -20,7 +27,11 @@ struct SystemPhotoCameraView: UIViewControllerRepresentable {
     }
 
     func makeCoordinator() -> Coordinator {
-        Coordinator(onMedia: onMedia, onCancel: onCancel)
+        Coordinator(
+            onDismissRequest: onDismissRequest,
+            onMedia: onMedia,
+            onCancel: onCancel
+        )
     }
 
     func makeUIViewController(context: Context) -> UIImagePickerController {
@@ -42,14 +53,17 @@ struct SystemPhotoCameraView: UIViewControllerRepresentable {
     ) {}
 
     final class Coordinator: NSObject, UIImagePickerControllerDelegate, UINavigationControllerDelegate {
+        private let onDismissRequest: () -> Void
         private let onMedia: (Result<CapturedCameraMedia, Error>) -> Void
         private let onCancel: () -> Void
         private var completed = false
 
         init(
+            onDismissRequest: @escaping () -> Void,
             onMedia: @escaping (Result<CapturedCameraMedia, Error>) -> Void,
             onCancel: @escaping () -> Void
         ) {
+            self.onDismissRequest = onDismissRequest
             self.onMedia = onMedia
             self.onCancel = onCancel
         }
@@ -60,6 +74,7 @@ struct SystemPhotoCameraView: UIViewControllerRepresentable {
         ) {
             guard !completed else { return }
             completed = true
+            onDismissRequest()
 
             let mediaType = (info[.mediaType] as? String).flatMap { UTType($0) }
             if mediaType?.conforms(to: .movie) == true,