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

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();
+}