feat(tutorial): add /tutorial/update_action fire-and-forget endpoint

Returns an empty data object (result_code=1 from middleware envelope).
Client uses SkipAllNetworkChecks so the response body is never read.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

SVSim.EmulatedEntrypoint/Models/Dtos/Requests/Tutorial/TutorialUpdateActionRequest.cs

@@ -0,0 +1,22 @@
+using System.Text.Json.Serialization;
+using MessagePack;
+using SVSim.EmulatedEntrypoint.Models.Dtos.Requests;
+
+namespace SVSim.EmulatedEntrypoint.Models.Dtos.Requests.Tutorial;
+
+/// <summary>
+/// <c>POST /tutorial/update_action</c> — fire-and-forget sub-step tracking.
+/// Client task: <c>Wizard/TutorialUpdateActionTask.cs</c>. SkipAllNetworkChecks is on,
+/// so any return value (including failures) is silently ignored.
+/// </summary>
+[MessagePackObject]
+public class TutorialUpdateActionRequest : BaseRequest
+{
+    [JsonPropertyName("tutorial_step")]
+    [Key("tutorial_step")]
+    public int TutorialStep { get; set; }
+
+    [JsonPropertyName("tutorial_action_number")]
+    [Key("tutorial_action_number")]
+    public int TutorialActionNumber { get; set; }
+}