[SPARK-56117] Make spotless ignore .claude directory

### What changes were proposed in this pull request?

This PR adds `.claude/**` to the Spotless `targetExclude` patterns in `build.gradle` for both Java formatting (in the `allprojects` block) and misc formatting (at the root level).

### Why are the changes needed?

The `.claude/` directory (used by Claude Code for worktrees, plans, and other metadata) contains files that should not be subject to Spotless formatting checks. Without this exclusion, Spotless may report false positives on files within `.claude/`.

### Does this PR introduce _any_ user-facing change?

No.

### How was this patch tested?

Pass the CIs and `gradle spotlessCheck` passes successfully.

BTW, the problem doesn't happen in the CI because it's a clean build without any Claude Code operations.

### Was this patch authored or co-authored using generative AI tooling?

Generated-by: Claude Code (Claude Opus 4.6)

Closes #566 from dongjoon-hyun/SPARK-56117.

Authored-by: Dongjoon Hyun <dongjoon@apache.org>
Signed-off-by: Dongjoon Hyun <dongjoon@apache.org>

Author: dongjoon-hyun

build.gradle

@@ -129,7 +129,7 @@ subprojects {
         'org.apache.spark',
       )
       toggleOffOn()
-      targetExclude "**/BaseResource.java"
+      targetExclude "**/BaseResource.java", ".claude/**"
       trimTrailingWhitespace()
       removeUnusedImports()
     }
@@ -140,7 +140,7 @@ apply plugin: 'com.diffplug.spotless'
 spotless {
   format 'misc', {
     target '*.md', '*.gradle', '**/*.properties', '**/*.xml', '**/*.yaml', '**/*.yml'
-    targetExclude "**/.idea/**"
+    targetExclude "**/.idea/**", ".claude/**"
     endWithNewline()
     trimTrailingWhitespace()
   }