updated to Paper 26.2, Java 25 and Gradle 9.6.1

- paper-api 26.2.build.129-stable (all modules), Java toolchain 25, shadow 9.6.1
- fixed NoSuchFieldError on join/quit/chat: Adventure 5 ClickEvent API
  (ClickEvent.suggestCommand / openUrl instead of ClickEvent.Action constants)
- fixed NBTComponent generics in AntiFormattedBook
- replaced javax.annotation with org.jetbrains.annotations (no longer provided by paper-api)
- local.gradle.example: Gradle 9 compatible (archiveFile, providers.exec)

The previous state is tagged as paper-1.21.10.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,6 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-8.5-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-9.6.1-bin.zip
 networkTimeout=10000
 validateDistributionUrl=true
 zipStoreBase=GRADLE_USER_HOME