feat(sleeve): /sleeve/favorite accept-only (persistence deferred)

SVSim.EmulatedEntrypoint/Controllers/SleeveController.cs

@@ -169,6 +169,16 @@ public class SleeveController : SVSimController
             .ToList();
     }
 
+    [HttpPost("favorite")]
+    public ActionResult<EmptyResponse> Favorite([FromBody] SleeveFavoriteRequest _)
+    {
+        if (!TryGetViewerId(out long __)) return Unauthorized();
+        // Accept-and-ack. Persisting per-viewer cosmetic favorites is deferred until
+        // a viewer-favorites schema lands (would also serve /emblem/favorite + /degree/favorite
+        // via the shared Wizard/FavoriteTask.cs Kind enum). Same pattern as ConfigController.
+        return new EmptyResponse();
+    }
+
     /// <summary>
     /// A product is "purchased" once the viewer owns at least one of its sleeve-typed reward
     /// grants. Emblem/other grants aren't load-bearing for this check — a viewer who somehow

SVSim.EmulatedEntrypoint/Models/Dtos/Requests/Sleeve/SleeveFavoriteRequest.cs

@@ -0,0 +1,18 @@
+using MessagePack;
+using System.Text.Json.Serialization;
+using SVSim.EmulatedEntrypoint.Models.Dtos.Requests;
+
+namespace SVSim.EmulatedEntrypoint.Models.Dtos.Requests.Sleeve;
+
+[MessagePackObject]
+public class SleeveFavoriteRequest : BaseRequest
+{
+    // Spec note: ids are STRINGS on the wire, not ints. Don't change to long[].
+    [JsonPropertyName("favorite_add")]
+    [Key("favorite_add")]
+    public List<string> FavoriteAdd { get; set; } = new();
+
+    [JsonPropertyName("favorite_remove")]
+    [Key("favorite_remove")]
+    public List<string> FavoriteRemove { get; set; } = new();
+}

SVSim.UnitTests/Controllers/SleeveControllerFavoriteTests.cs

@@ -0,0 +1,44 @@
+using System.Net;
+using System.Text;
+using NUnit.Framework;
+using SVSim.UnitTests.Infrastructure;
+
+namespace SVSim.UnitTests.Controllers;
+
+public class SleeveControllerFavoriteTests
+{
+    [Test]
+    public async Task Favorite_accepts_add_and_remove_lists()
+    {
+        using var factory = new SVSimTestFactory();
+        long viewerId = await factory.SeedViewerAsync(tutorialState: 0);
+        using var client = factory.CreateAuthenticatedClient(viewerId);
+
+        // Stringified ids per spec.
+        var requestJson = """
+        {
+            "favorite_add":["100","101"],
+            "favorite_remove":["200"],
+            "viewer_id":"0","steam_id":0,"steam_session_ticket":""
+        }
+        """;
+        var response = await client.PostAsync("/sleeve/favorite",
+            new StringContent(requestJson, Encoding.UTF8, "application/json"));
+
+        Assert.That(response.StatusCode, Is.EqualTo(HttpStatusCode.OK));
+    }
+
+    [Test]
+    public async Task Favorite_accepts_empty_lists()
+    {
+        using var factory = new SVSimTestFactory();
+        long viewerId = await factory.SeedViewerAsync(tutorialState: 0);
+        using var client = factory.CreateAuthenticatedClient(viewerId);
+
+        var requestJson = """{"favorite_add":[],"favorite_remove":[],"viewer_id":"0","steam_id":0,"steam_session_ticket":""}""";
+        var response = await client.PostAsync("/sleeve/favorite",
+            new StringContent(requestJson, Encoding.UTF8, "application/json"));
+
+        Assert.That(response.StatusCode, Is.EqualTo(HttpStatusCode.OK));
+    }
+}