test(m9): replace MainActor.assertIsolated for Swift 5.7 (#115)

MainActor.assertIsolated() requires Swift 5.9 (Xcode 15); the macOS 12
CI runner compiles the test bundle with Swift 5.7 and failed run 31985.
Assert Thread.isMainThread instead — it checks the same contract (the
coalesced log sink hops back to the main actor).

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Sources/ICCery/Print/PrintSessionViewModel.swift

@@ -110,7 +110,8 @@ final class PrintSessionViewModel: ObservableObject {
         isPrinting = true
         let task = Task { @MainActor [weak self] in
             guard let self else { return }
-            defer { self.printTask = nil }
+            // `defer` cannot mutate isolated state under Swift 5.7
+            // (Xcode 14.2 / macOS 12 runner), so clear explicitly (#113).
             var printed = 0
             for page in result.pages {
                 do {
@@ -123,6 +124,7 @@ final class PrintSessionViewModel: ObservableObject {
                             + error.localizedDescription
                     )
                     isPrinting = false
+                    self.printTask = nil
                     return
                 }
             }
@@ -132,6 +134,7 @@ final class PrintSessionViewModel: ObservableObject {
                 autoHideAfter: nil
             )
             isPrinting = false
+            self.printTask = nil
         }
         printTask = task
     }
@@ -141,7 +144,6 @@ final class PrintSessionViewModel: ObservableObject {
         isPrinting = true
         let task = Task { @MainActor [weak self] in
             guard let self else { return }
-            defer { self.printTask = nil }
             do {
                 try await spool(page, index: page.index, pageSize: pageSize)
                 printNotice = Notice(
@@ -156,6 +158,7 @@ final class PrintSessionViewModel: ObservableObject {
                 )
             }
             isPrinting = false
+            self.printTask = nil
         }
         printTask = task
     }

Sources/ICCery/Stage4View.swift

@@ -138,16 +138,20 @@ struct Stage4View: View {
                 .textFieldStyle(.roundedBorder)
                 .accessibilityIdentifier("colprofCopyright")
 
-            Toggle("Apply calibration curve", isOn: $model.applyCalibration)
+            // Nested VStack keeps the parent at the Swift 5.7 ViewBuilder
-                .accessibilityIdentifier("colprofApplyCalibration")
+            // 10-child limit (Xcode 14.2 / macOS 12 CI runner, #111).
+            VStack(alignment: .leading, spacing: 12) {
+                Toggle("Apply calibration curve", isOn: $model.applyCalibration)
+                    .accessibilityIdentifier("colprofApplyCalibration")
 
-            if model.applyCalibration {
+                if model.applyCalibration {
-                HStack {
+                    HStack {
-                    TextField("Calibration .cal file", text: $model.calibrationFile)
+                        TextField("Calibration .cal file", text: $model.calibrationFile)
-                        .textFieldStyle(.roundedBorder)
+                            .textFieldStyle(.roundedBorder)
-                        .accessibilityIdentifier("colprofCalibrationFile")
+                            .accessibilityIdentifier("colprofCalibrationFile")
-                    Button("Browse…") { model.browseForCalibrationFile() }
+                        Button("Browse…") { model.browseForCalibrationFile() }
-                        .accessibilityIdentifier("btnBrowseCalibrationFile")
+                            .accessibilityIdentifier("btnBrowseCalibrationFile")
+                    }
                 }
             }
         }

Tests/ICCeryCoreTests/ProcessRunSupportTests.swift

@@ -21,7 +21,9 @@ final class ProcessRunSupportTests: XCTestCase {
             setRunning: { running.append($0) },
             resetLog: { resets += 1 },
             onLog: { batch in
-                MainActor.assertIsolated()
+                // MainActor.assertIsolated() needs Swift 5.9; the runner is
+                // on Xcode 14.2 (Swift 5.7) (#115).
+                XCTAssertTrue(Thread.isMainThread)
                 received.append(contentsOf: batch)
             }
         ) { onLog in