Deck list work

SVSim.EmulatedEntrypoint/Models/Dtos/GatheringNotification.cs

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+using MessagePack;
+using System.Text.Json.Serialization;
+
+namespace SVSim.EmulatedEntrypoint.Models.Dtos;
+
+/// <summary>
+/// gathering_notification on /mypage/refresh — slim "matching established?" notification flag for
+/// gathering events. Single field carrying either an empty string (no match) or the localized
+/// "matching established" message (active match).
+///
+/// **Distinct from <see cref="GatheringInfo"/>**, which is what /mypage/index emits under the
+/// <c>gathering_info</c> key — that DTO carries the viewer's full event participation state
+/// (has_invite / is_entry). They share a topic ("gathering events") but solve different problems
+/// and live at different wire keys; don't conflate them.
+///
+/// Consumed unconditionally at <c>MyPageRefreshTask.cs:31</c>:
+/// <c>jsonData["data"]["gathering_notification"]["matching_established_message"].ToString()</c>.
+/// </summary>
+[MessagePackObject]
+public class GatheringNotification
+{
+    /// <summary>Empty string when no match — correct for fresh viewers and idle states. Prod sends "".</summary>
+    [JsonPropertyName("matching_established_message")]
+    [Key("matching_established_message")]
+    public string MatchingEstablishedMessage { get; set; } = string.Empty;
+}