Moving the copilot-sdk cookbook content in here

cookbook/copilot-sdk/dotnet/recipe/error-handling.cs

@@ -0,0 +1,38 @@
+#:package GitHub.Copilot.SDK@*
+#:property PublishAot=false
+
+using GitHub.Copilot.SDK;
+
+var client = new CopilotClient();
+
+try
+{
+    await client.StartAsync();
+    var session = await client.CreateSessionAsync(new SessionConfig
+    {
+        Model = "gpt-5"
+    });
+
+    var done = new TaskCompletionSource<string>();
+    session.On(evt =>
+    {
+        if (evt is AssistantMessageEvent msg)
+        {
+            done.SetResult(msg.Data.Content);
+        }
+    });
+
+    await session.SendAsync(new MessageOptions { Prompt = "Hello!" });
+    var response = await done.Task;
+    Console.WriteLine(response);
+
+    await session.DisposeAsync();
+}
+catch (Exception ex)
+{
+    Console.WriteLine($"Error: {ex.Message}");
+}
+finally
+{
+    await client.StopAsync();
+}