Command refactor

src/AppCommon/FileTime.App.Core.Abstraction/UserCommand/CloseTabCommand.cs

@@ -0,0 +1,13 @@
+namespace FileTime.App.Core.UserCommand;
+
+public class CloseTabCommand : IIdentifiableUserCommand
+{
+    public const string CommandName = "close_tab";
+    public static CloseTabCommand Instance { get; } = new CloseTabCommand();
+
+    private CloseTabCommand()
+    {
+    }
+
+    public string UserCommandID => CommandName;
+}