Fix CI: jdk24 case duplicate and Snippets license headers

- JavaSourceLevel.swift: rename duplicated 'case jdk24 = 25' to
  'case jdk25 = 25'. The typo broke RawRepresentable synthesis and
  cascaded into every Swift build/test/sample job.
- Add Apache-2.0 header to Snippets/NotSupportedYetJava{FFM,JNI}.java.
- Ignore Snippets/__DO_NOT_EDIT_SYMLINK_ONLY__ in .licenseignore
  (extensionless marker file the license-check script can't classify).

Author: ktoso

.licenseignore

@@ -45,6 +45,7 @@ gradlew.bat
 **/gradlew.bat
 **/ci-validate.sh
 **/DO_NOT_EDIT.txt
+Snippets/__DO_NOT_EDIT_SYMLINK_ONLY__
 Plugins/**/_PluginsShared
 Plugins/**/0_PLEASE_SYMLINK*
 Plugins/PluginsShared/JavaKitConfigurationShared

Snippets/NotSupportedYetJavaFFM.java

@@ -1,3 +1,17 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2025 Apple Inc. and the Swift.org project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of Swift.org project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
 // This file is an intentional exception to the "Snippets/ is symlink-only" rule
 // documented in Snippets/__DO_NOT_EDIT_SYMLINK_ONLY__ . It is a pedagogical
 // placeholder for @Tab("Java (FFM) - not supported") blocks in the DocC pages.

Snippets/NotSupportedYetJavaJNI.java

@@ -1,3 +1,17 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2025 Apple Inc. and the Swift.org project authors
+// Licensed under Apache License v2.0
+//
+// See LICENSE.txt for license information
+// See CONTRIBUTORS.txt for the list of Swift.org project authors
+//
+// SPDX-License-Identifier: Apache-2.0
+//
+//===----------------------------------------------------------------------===//
+
 // This file is an intentional exception to the "Snippets/ is symlink-only" rule
 // documented in Snippets/__DO_NOT_EDIT_SYMLINK_ONLY__ . It is a pedagogical
 // placeholder for @Tab("Java (JNI) - not supported") blocks in the DocC pages.

Sources/SwiftJavaConfigurationShared/JExtract/JavaSourceLevel.swift

@@ -22,7 +22,7 @@ public enum JavaSourceLevel: Int, Comparable, Sendable {
   case jdk21 = 21
   case jdk22 = 22
   case jdk24 = 24
-  case jdk24 = 25
+  case jdk25 = 25
 
   public static var `default`: Self { .jdk22 }