fix(m9): keep Stage4View under Swift 5.7 ViewBuilder 10-child limit (#111)

The formSection VStack had 11 direct children; Xcode 14.2's ViewBuilder
only provides buildBlock overloads up to 10 arguments, so the CI build
on the macOS 12 runner failed at line 144 with "extra argument in call"
(run 31958). Nest the calibration toggle and conditional file row in an
inner VStack with identical alignment and spacing.

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Sources/ICCery/Stage4View.swift

@@ -138,16 +138,20 @@ struct Stage4View: View {
                 .textFieldStyle(.roundedBorder)
                 .accessibilityIdentifier("colprofCopyright")
 
-            Toggle("Apply calibration curve", isOn: $model.applyCalibration)
-                .accessibilityIdentifier("colprofApplyCalibration")
+            // Nested VStack keeps the parent at the Swift 5.7 ViewBuilder
+            // 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 {
-                HStack {
-                    TextField("Calibration .cal file", text: $model.calibrationFile)
-                        .textFieldStyle(.roundedBorder)
-                        .accessibilityIdentifier("colprofCalibrationFile")
-                    Button("Browse…") { model.browseForCalibrationFile() }
-                        .accessibilityIdentifier("btnBrowseCalibrationFile")
+                if model.applyCalibration {
+                    HStack {
+                        TextField("Calibration .cal file", text: $model.calibrationFile)
+                            .textFieldStyle(.roundedBorder)
+                            .accessibilityIdentifier("colprofCalibrationFile")
+                        Button("Browse…") { model.browseForCalibrationFile() }
+                            .accessibilityIdentifier("btnBrowseCalibrationFile")
+                    }
                 }
             }
         }