Deck list work

SVSim.EmulatedEntrypoint/Models/Dtos/Convention.cs

@@ -16,11 +16,16 @@ public class Convention
     public bool IsJoinTournament { get; set; }
 
     /// <summary>
-    /// ISO datetime. Optional — omitted via WhenWritingNull when not set.
-    /// Client null-checks before parsing (MyPageTask.cs:59).
+    /// ISO datetime, or null when no recent tournament. Client does
+    /// `if (jsonData["convention"]["recent_start_date"] != null)` (MyPageTask.cs:59) —
+    /// the key must be PRESENT (LitJson throws KeyNotFoundException on missing key);
+    /// the null check exists to detect "no recent tournament", not "field absent".
+    /// Override the global WhenWritingNull so the explicit null reaches the wire,
+    /// matching prod's `"recent_start_date":null` in the convention block.
     /// </summary>
     [JsonPropertyName("recent_start_date")]
     [Key("recent_start_date")]
+    [JsonIgnore(Condition = JsonIgnoreCondition.Never)]
     public string? RecentStartDate { get; set; }
 
     [JsonPropertyName("is_admin_watch_user")]