Add /kuvel admin command for server registration visibility, edits, and repair

[Copilot]

この変更は、Velocity 上でサーバー登録状態を運用者が直接確認・修正できるようにするため、/kuvel 管理コマンドを追加するものです。
登録状態の可視化に加え、手動登録/解除・名前変更・整合性修復をコマンド経由で実行できるようにしています。

• Command entrypoint

  • Kuvel 初期化時に /kuvel を登録
  • 新規 KuvelCommand を追加（SimpleCommand 実装、kuvel.command 権限）

• Operational subcommands

  • status: リーダー状態、pod/load balancer のマッピング数、不足登録数を表示
  • list <pods|loadbalancers>: UID → server name マッピング一覧を表示
  • register <podUid> <serverName>: Pod の手動登録
  • unregister <podUid>: Pod の手動解除
  • setname <podUid> <serverName>: 既存 Pod の登録名変更
  • repair: 欠落登録の再試行と壊れたマッピングのクリーンアップ

• Conflict/edge-case handling

  • 既存 UID マッピングとの衝突を検知して登録を拒否
  • setname の no-op（同名再設定）を明示的に扱う
  • 修復処理で登録成否を boolean で判定できるようにし、失敗時の誤判定を回避

• Core API adjustment (minimal)

  • KuvelServiceHandler#registerPod(String podUid, String serverName) を boolean 戻り値化し、コマンド側の成否判定に利用

• Documentation

  • README.md / README-JP.md に /kuvel コマンド一覧と用途を追記

proxy
    .getCommandManager()
    .register(
        proxy.getCommandManager().metaBuilder("kuvel").plugin(this).build(),
        new KuvelCommand(this));

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• repo.papermc.io
  • Triggering command: /usr/lib/jvm/temurin-17-jdk-amd64/bin/java /usr/lib/jvm/temurin-17-jdk-amd64/bin/java --enable-native-access=ALL-UNNAMED -classpath /usr/share/apache-maven-3.9.12/boot/plexus-classworlds-2.9.0.jar -Dclassworlds.conf=/usr/share/apache-maven-3.9.12/bin/m2.conf -Dmaven.home=/usr/share/apache-maven-3.9.12 -Dlibrary.jansi.path=/usr/share/apache-maven-3.9.12/lib/jansi-native -Dmaven.multiModuleProjectDirectory=/home/REDACTED/work/Kuvel/Kuvel org.codehaus.plexus.classworlds.launcher.Launcher -B package (dns block)
  • Triggering command: /usr/lib/jvm/temurin-17-jdk-amd64/bin/java /usr/lib/jvm/temurin-17-jdk-amd64/bin/java --enable-native-access=ALL-UNNAMED -classpath /usr/share/apache-maven-3.9.12/boot/plexus-classworlds-2.9.0.jar -Dclassworlds.conf=/usr/share/apache-maven-3.9.12/bin/m2.conf -Dmaven.home=/usr/share/apache-maven-3.9.12 -Dlibrary.jansi.path=/usr/share/apache-maven-3.9.12/lib/jansi-native -Dmaven.multiModuleProjectDirectory=/home/REDACTED/work/Kuvel/Kuvel org.codehaus.plexus.classworlds.launcher.Launcher -f pom.xml -B -V -e -Dfindbugs.skip -Dcheckstyle.skip -Dpmd.skip=true -Dspotbugs.skip -Denforcer.skip -Dmaven.javadoc.skip (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

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