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

ChatSession.cs

@@ -1,4 +1,5 @@
 using Microsoft.Extensions.AI;
+using System.Text.Json;
 
 namespace AnchorCli;
 
@@ -69,4 +70,38 @@ internal sealed class ChatSession
             yield return update;
         }
     }
+
+    public async Task SaveAsync(string filePath, CancellationToken cancellationToken = default)
+    {
+        // Skip the system message when saving (it will be recreated on load)
+        var messagesToSave = History.Skip(1).ToList();
+        
+        var options = new JsonSerializerOptions
+        {
+            PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
+            WriteIndented = true
+        };
+        
+        var json = JsonSerializer.Serialize(messagesToSave, AppJsonContext.Default.ListChatMessage);
+        await File.WriteAllTextAsync(filePath, json, cancellationToken);
+    }
+
+    public async Task LoadAsync(string filePath, CancellationToken cancellationToken = default)
+    {
+        var json = await File.ReadAllTextAsync(filePath, cancellationToken);
+        
+        var options = new JsonSerializerOptions
+        {
+            PropertyNamingPolicy = JsonNamingPolicy.CamelCase
+        };
+        
+        var messages = JsonSerializer.Deserialize<List<ChatMessage>>(json, AppJsonContext.Default.ListChatMessage)
+            ?? new List<ChatMessage>();
+        
+        // Keep the system message and append loaded messages
+        var systemMessage = History[0];
+        History.Clear();
+        History.Add(systemMessage);
+        History.AddRange(messages);
+    }
 }