Fix decoder state restoration after decoding child

Sources/Library/Serialization/Decoder.swift

@@ -30,7 +30,7 @@ extension XCJSON {
             let oldPath = currentPath; defer {
                 currentPath = oldPath
             }
-            let oldCurrentValue = value; defer {
+            let oldCurrentValue = currentValue; defer {
                 currentValue = oldCurrentValue
             }
             let newPath = AbsolutePath(parent: oldPath, component: pathComponent)

Sources/Tests/DecoderStateTests.swift

@@ -0,0 +1,27 @@
+//===----------------------------------------------------------------------===//
+// Copyright © 2026 Apple Inc. and the xcode-project-format project authors
+//
+// Licensed under Apache License v2.0 with Runtime Library Exception
+// SPDX-License-Identifier: Apache-2.0 WITH Swift-exception
+//
+//===----------------------------------------------------------------------===//
+
+import Foundation
+import Testing
+import XcodeProjectFormat
+
+private struct ParentValueProbe: XCJSON.Decodable {
+    init(with coder: XCJSON.Decoder) throws {
+        let container = try coder.openKeyedContainer()
+        let _: String = try container.decode("name")
+
+        #expect(coder.currentNodeType == .object)
+        _ = try coder.openKeyedContainer()
+    }
+}
+
+@Test func restoresParentValueAfterDecodingChild() throws {
+    let _: ParentValueProbe = try XCJSON.Decoder.decode(
+        data: Data(#"{"name":"App"}"#.utf8)
+    )
+}