Move compound-ios package into the project.

compound-ios/Sources/Compound/Previews/Snapshotting.swift

@@ -0,0 +1,42 @@
+// 
+// Copyright 2025 New Vector Ltd
+//
+// SPDX-License-Identifier: AGPL-3.0-only
+// Please see LICENSE in the repository root for full details.
+//
+
+import Combine
+import SwiftUI
+
+struct SnapshotPrecisionPreferenceKey: PreferenceKey {
+    static var defaultValue: Float = 1.0
+
+    static func reduce(value: inout Float, nextValue: () -> Float) {
+        value = nextValue()
+    }
+}
+
+struct SnapshotPerceptualPrecisionPreferenceKey: PreferenceKey {
+    static var defaultValue: Float = 0.98
+
+    static func reduce(value: inout Float, nextValue: () -> Float) {
+        value = nextValue()
+    }
+}
+
+extension SwiftUI.View {
+    /// Use this modifier when you want to apply snapshot-specific preferences,
+    /// like delay and precision, to the view.
+    /// These preferences can then be retrieved and used elsewhere in your view hierarchy.
+    ///
+    /// - Parameters:
+    ///   - delay: The delay time in seconds that you want to set as a preference to the View.
+    ///   - precision: The percentage of pixels that must match.
+    ///   - perceptualPrecision: The percentage a pixel must match the source pixel to be considered a match. 98-99% mimics the precision of the human eye.
+    func snapshotPreferences(expect fulfillmentPublisher: (any Publisher<Bool, Never>)? = nil,
+                             precision: Float = 1.0,
+                             perceptualPrecision: Float = 0.98) -> some SwiftUI.View {
+        preference(key: SnapshotPrecisionPreferenceKey.self, value: precision)
+            .preference(key: SnapshotPerceptualPrecisionPreferenceKey.self, value: perceptualPrecision)
+    }
+}

compound-ios/Sources/Compound/Previews/TestablePreview.swift

@@ -0,0 +1,8 @@
+// 
+// Copyright 2025 New Vector Ltd
+//
+// SPDX-License-Identifier: AGPL-3.0-only
+// Please see LICENSE in the repository root for full details.
+//
+
+protocol TestablePreview { }