Deck list work

SVSim.EmulatedEntrypoint/Models/Dtos/SealedSalesPeriodInfo.cs

@@ -0,0 +1,17 @@
+using MessagePack;
+using System.Text.Json.Serialization;
+
+namespace SVSim.EmulatedEntrypoint.Models.Dtos;
+
+/// <summary>
+/// Nested under /mypage/index data.sealed_info.sales_period_info. Distinct from Arena/Colosseum's
+/// sales_period_info shapes — this inner value is an int (the active schedule series number),
+/// not a date string. Captured from prod: <c>"sales_period_info": { "sales_period_series": 33 }</c>.
+/// </summary>
+[MessagePackObject]
+public class SealedSalesPeriodInfo
+{
+    [JsonPropertyName("sales_period_series")]
+    [Key("sales_period_series")]
+    public int SalesPeriodSeries { get; set; }
+}