Add /clear as an alias to /cls (#370)

Author: daxian-dbw

shell/AIShell.Kernel/Command/ClearCommand.cs

@@ -6,9 +6,10 @@ namespace AIShell.Kernel.Commands;
 internal sealed class ClearCommand : CommandBase
 {
     public ClearCommand()
-        : base("cls", "Clear the screen.")
+        : base("clear", "Clear the screen.")
     {
         this.SetHandler(ClearAction);
+        this.AddAlias("cls");
     }
 
     private void ClearAction()

shell/AIShell.Kernel/Command/CommandRunner.cs

@@ -57,7 +57,14 @@ internal void LoadCommands(IEnumerable<CommandBase> commands, string agentName)
         {
             command.Shell = _shell;
             command.Source = agentName;
-            _commands.Add(command.Name, command);
+
+            // The 'command.Name' is included in the 'command.Aliases' collection.
+            // TODO: need to think about how to handle command names/aliases collision.
+            // We don't handle collision today -- it will throw when collision happens.
+            foreach (string alias in command.Aliases)
+            {
+                _commands.Add(alias, command);
+            }
         }
     }
 
@@ -79,7 +86,13 @@ internal void UnloadAgentCommands()
 
         foreach (var command in agentCommands)
         {
-            _commands.Remove(command.Name);
+            // The 'command.Name' is included in the 'command.Aliases' collection.
+            // TODO: need to update accordingly when we handle command names/aliases collision.
+            foreach (string alias in command.Aliases)
+            {
+                _commands.Remove(alias);
+            }
+
             command.Dispose();
         }
     }

shell/AIShell.Kernel/Command/HelpCommand.cs

@@ -17,7 +17,7 @@ private void HelpAction()
         var host = shellImpl.Host;
 
         var commands = shellImpl.CommandRunner.Commands;
-        var list = commands.Values.Order(new CommandComparer()).ToList();
+        var list = commands.Values.Distinct().Order(new CommandComparer()).ToList();
 
         host.WriteLine();
         host.MarkupLine("[bold white]-[/] Type then press [bold olive underline]Enter[/] to chat with the chosen AI agent.");