[ZEPPELIN-6405] Add Apache License header to AGENTS.md and revert RAT exclusion

Add the standard ASF license header to AGENTS.md instead of excluding
it from the RAT license check.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: jongyoul

AGENTS.md

@@ -1,3 +1,20 @@
+<!--
+Licensed to the Apache Software Foundation (ASF) under one or more
+contributor license agreements.  See the NOTICE file distributed with
+this work for additional information regarding copyright ownership.
+The ASF licenses this file to You 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
+
+   http://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.
+-->
+
 # AGENTS.md
 
 > Guidance for AI coding agents working on the Apache Zeppelin codebase.

pom.xml

@@ -950,7 +950,6 @@
               <exclude>.github/</exclude>
               <exclude>.gitignore</exclude>
               <exclude>.gitattributes</exclude>
-              <exclude>AGENTS.md</exclude>
               <exclude>git.properties</exclude>
               <exclude>.repository/</exclude>
               <exclude>.rat-excludes/</exclude>