chore: import upstream snapshot with attribution

Sources/Containerization/VirtualMachineManager.swift

@@ -0,0 +1,20 @@
+//===----------------------------------------------------------------------===//
+// 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.
+//===----------------------------------------------------------------------===//
+
+/// A protocol to implement for virtual machine isolated containers.
+public protocol VirtualMachineManager: Sendable {
+    func create(config: some VMCreationConfig) async throws -> any VirtualMachineInstance
+}