chore: import upstream snapshot with attribution

Sources/ContainerXPC/XPCServerSession.swift

@@ -0,0 +1,50 @@
+//===----------------------------------------------------------------------===//
+// Copyright © 2026 Apple Inc. and the container 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.
+//===----------------------------------------------------------------------===//
+
+#if os(macOS)
+
+/// Represents a single client connection on the server side.
+///
+/// The server creates one `XPCServerSession` per accepted client connection.
+/// Handlers that need to associate state with a connection (e.g. resource
+/// tracking for automatic cleanup) receive the session as a parameter and
+/// may register disconnect handlers via `onDisconnect(_:)`.
+public actor XPCServerSession {
+    private var disconnectHandlers: [@Sendable () async -> Void] = []
+
+    public init() {}
+
+    /// Register a handler to be called when the client connection closes.
+    public func onDisconnect(_ handler: @Sendable @escaping () async -> Void) {
+        disconnectHandlers.append(handler)
+    }
+
+    func fireDisconnect() async {
+        for handler in disconnectHandlers { await handler() }
+    }
+}
+
+extension XPCServerSession: Hashable {
+    public nonisolated static func == (lhs: XPCServerSession, rhs: XPCServerSession) -> Bool {
+        lhs === rhs
+    }
+
+    public nonisolated func hash(into hasher: inout Hasher) {
+        hasher.combine(ObjectIdentifier(self))
+    }
+}
+
+#endif