Nucleic: Gitea Runner macOS VM Support

Sources/RunnerHost/ImageBuilder.swift

@@ -6,10 +6,16 @@ import Virtualization
 public enum ImageBuildStage: Sendable, Equatable {
     /// Downloading the IPSW.
     case downloadingIPSW(fraction: Double)
-    /// Reading the restore image and deriving a hardware configuration.
+    /// Working out which file the operator meant and whether it is usable.
     case preparing
+    /// Inside `VZMacOSRestoreImage.image(from:)`, which reports no progress of
+    /// its own and is the longest silent stretch of a local-IPSW build.
+    case loadingRestoreImage
     /// Creating the disk, NVRAM, and bundle metadata.
-    case creatingBundle
+    case creatingBundle(diskGB: Int)
+    /// An out-of-band remark about the stage in flight — printed on its own
+    /// line rather than replacing the status line.
+    case note(String)
     /// `VZMacOSInstaller` is writing macOS onto the disk.
     case installing(fraction: Double)
     /// First boot; waiting for Setup Assistant, a DHCP lease, and SSH.
@@ -89,7 +95,28 @@ public struct ImageBuilder: Sendable {
         let provider = IPSWProvider(downloadDirectory: store.ipswDir)
         let restoreImage: VZMacOSRestoreImage
         if let ipswPath {
-            progress?(.downloadingIPSW(fraction: 1.0))
+            progress?(.preparing)
+            progress?(.loadingRestoreImage)
+
+            // Reading a 21 GB archive's metadata takes a while and the
+            // framework says nothing while it does. A build that looks frozen
+            // is the single most-reported symptom of this command, so say out
+            // loud what the other likely explanation is rather than letting the
+            // operator guess.
+            let watchdog = Task {
+                try? await Task.sleep(for: .seconds(60))
+                // Cancelling is how a *fast* load ends this task, and a
+                // cancelled sleep returns rather than throwing past `try?` — so
+                // without this the note prints on every quick failure, which is
+                // precisely when it is misleading.
+                guard !Task.isCancelled else { return }
+                progress?(
+                    .note(
+                        "still loading — a truncated or partially downloaded .ipsw can block here; "
+                            + "verify the download completed"))
+            }
+            defer { watchdog.cancel() }
+
             restoreImage = try await provider.load(localPath: ipswPath)
         } else {
             progress?(.downloadingIPSW(fraction: 0))
@@ -100,8 +127,7 @@ public struct ImageBuilder: Sendable {
         }
 
         // 2/3. Hardware model and bundle.
-        progress?(.preparing)
-        progress?(.creatingBundle)
+        progress?(.creatingBundle(diskGB: config.guest.diskGB))
         let bundle = try await createBundle(name: name, restoreImage: restoreImage, config: config)
 
         // 4. Install.