chore: import upstream snapshot with attribution

Sources/Containerization/SystemPlatform.swift

@@ -0,0 +1,41 @@
+//===----------------------------------------------------------------------===//
+// Copyright © 2025-2026 Apple Inc. and the Containerization project authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//   https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//===----------------------------------------------------------------------===//
+
+import ContainerizationOCI
+
+/// `SystemPlatform` describes an operating system and architecture pair.
+/// This is primarily used to choose what kind of OCI image to pull from a
+/// registry.
+public struct SystemPlatform: Sendable, Codable {
+    public enum OS: String, CaseIterable, Sendable, Codable {
+        case linux
+        case darwin
+    }
+    public let os: OS
+
+    public enum Architecture: String, CaseIterable, Sendable, Codable {
+        case arm64
+        case amd64
+    }
+    public let architecture: Architecture
+
+    public func ociPlatform() -> ContainerizationOCI.Platform {
+        ContainerizationOCI.Platform(arch: architecture.rawValue, os: os.rawValue)
+    }
+
+    public static var linuxArm: SystemPlatform { .init(os: .linux, architecture: .arm64) }
+    public static var linuxAmd: SystemPlatform { .init(os: .linux, architecture: .amd64) }
+}