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/Controllers/TutorialController.cs

@@ -0,0 +1,19 @@
+using Microsoft.AspNetCore.Mvc;
+using SVSim.EmulatedEntrypoint.Models.Dtos.Requests.Tutorial;
+
+namespace SVSim.EmulatedEntrypoint.Controllers;
+
+/// <summary>
+/// Tutorial step bookkeeping. The tutorial itself runs entirely client-side
+/// (StoryTutorial*BattleMgr per class); the server only persists step transitions.
+/// </summary>
+public class TutorialController : SVSimController
+{
+    [HttpPost("update_action")]
+    public IActionResult UpdateAction([FromBody] TutorialUpdateActionRequest request)
+    {
+        // Fire-and-forget. Client uses SkipAllNetworkChecks; response body is ignored.
+        // We still emit an empty object so the translation middleware has a `data` payload to wrap.
+        return new JsonResult(new { });
+    }
+}