Wallets: expected-days drain, copy/paste, three-column selectable balances, rename and destroy

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

src/Decentralized/Core.cs

@@ -29,6 +29,13 @@ namespace Decentralized
         }
     }
 
+    /// <summary>系统剪贴板（游戏里的输入框也能 Ctrl+V）。</summary>
+    public static class Clipboard
+    {
+        public static void Copy(string s) => GUIUtility.systemCopyBuffer = s ?? "";
+        public static string Paste() => (GUIUtility.systemCopyBuffer ?? "").Trim();
+    }
+
     public static class Fmt
     {
         public static string Num(double v) => Math.Abs(v) >= 100 ? v.ToString("N0") : Math.Abs(v) >= 1 ? v.ToString("0.##") : v.ToString("0.####");