docs: add native Japanese translation of ECC documentation (ja-JP)

Translate everything-claude-code repository to Japanese including:
- 17 root documentation files
- 60 agent documentation files
- 80 command documentation files
- 99 rule files across 18 language directories (common, angular, arkts, cpp, csharp, dart, fsharp, golang, java, kotlin, perl, php, python, ruby, rust, swift, typescript, web)
- 199 skill documentation files

Total: 455 files translated to Japanese with:
- Consistent terminology glossary applied throughout
- YAML field names preserved in English (name, description, etc.)
- Code blocks and examples untouched (comments translated)
- Markdown structure and relative links preserved
- Professional translation maintaining technical accuracy

This translation expands ECC accessibility to Japanese-speaking developers and teams.

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

docs/ja-JP/rules/java/hooks.md

@@ -0,0 +1,18 @@
+---
+paths:
+  - "**/*.java"
+  - "**/pom.xml"
+  - "**/build.gradle"
+  - "**/build.gradle.kts"
+---
+# Java フック
+
+> このファイルは [common/hooks.md](../common/hooks.md) を Java 固有のコンテンツで拡張します。
+
+## PostToolUse フック
+
+`~/.claude/settings.json` で設定:
+
+- **google-java-format**: 編集後に `.java` ファイルを自動フォーマット
+- **checkstyle**: Java ファイル編集後にスタイルチェックを実行
+- **./mvnw compile** または **./gradlew compileJava**: 変更後にコンパイルを検証