feat: Add commands and functionality to save and load chat sessions.

Commands/SaveCommand.cs

@@ -0,0 +1,31 @@
+using Spectre.Console;
+
+namespace AnchorCli.Commands;
+
+internal class SaveCommand(ChatSession session) : ICommand
+{
+    public string Name => "save";
+    public string Description => "Save the current chat session to a file";
+
+    public async Task ExecuteAsync(string[] args, CancellationToken ct)
+    {
+        string filePath = args.Length > 0 ? args[0] : ".anchor/session.json";
+
+        try
+        {
+            var directory = Path.GetDirectoryName(filePath);
+            if (!string.IsNullOrEmpty(directory) && !Directory.Exists(directory))
+            {
+                Directory.CreateDirectory(directory);
+            }
+
+            await session.SaveAsync(filePath, ct);
+            AnsiConsole.MarkupLine($"[green]Session saved to {Markup.Escape(filePath)}[/]");
+        }
+        catch (Exception ex)
+        {
+            AnsiConsole.MarkupLine($"[red]Failed to save session: {Markup.Escape(ex.Message)}[/]");
+        }
+    }
+}
+