feat: Introduce a /reset command to clear the chat session and token tracking, and update documentation.

Commands/ResetCommand.cs

@@ -0,0 +1,21 @@
+using Microsoft.Extensions.AI;
+using Spectre.Console;
+using AnchorCli.OpenRouter;
+
+namespace AnchorCli.Commands;
+
+internal class ResetCommand(ChatSession session, TokenTracker tokenTracker) : ICommand
+{
+    public string Name => "reset";
+    public string Description => "Reset the chat session (clear history and token count)";
+
+    public Task ExecuteAsync(string[] args, CancellationToken ct)
+    {
+        session.Reset();
+        tokenTracker.Reset();
+        AnsiConsole.MarkupLine("[green]Chat session reset.[/]");
+        return Task.CompletedTask;
+    }
+}
+
+