review(bp): doc fixes + sales_period_info non-nullable + drop checked cast + TODO

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

SVSim.Database/Repositories/BattlePass/IViewerBattlePassRepository.cs

@@ -6,8 +6,10 @@ namespace SVSim.Database.Repositories.BattlePass;
 public interface IViewerBattlePassRepository
 {
     /// <summary>
-    /// Get-or-create progress row for (viewer, season). New rows are added to the change-tracker
+    /// Get-or-create progress row for (viewer, season). New rows are saved IMMEDIATELY (with
-    /// but NOT saved — caller batches with other mutations.
+    /// DbUpdateException catch-and-retry to handle the concurrent-first-visit race against
+    /// the (ViewerId, SeasonId) unique index). Existing rows are returned tracked so callers
+    /// can mutate them and batch the save with other changes.
     /// </summary>
     Task<ViewerBattlePassProgressEntry> GetOrCreateProgressAsync(long viewerId, int seasonId, CancellationToken ct);
 

SVSim.EmulatedEntrypoint/Controllers/BattlePassController.cs

@@ -25,7 +25,12 @@ public class BattlePassController : SVSimController
         if (!TryGetViewerId(out long viewerId)) return Unauthorized();
 
         var info = await _battlePass.GetInfoAsync(viewerId, ct);
-        if (info is null) return Ok(new { }); // off-season: empty payload
+        // TODO(off-season-crash): Empty {} body crashes BattlePassInfoTask.Parse() on the
+        // client (unconditional jsonData["season_info"] access). Unreachable in practice —
+        // season 23 outlasts the Cygames shutdown. If a season-24+ ever lands, set
+        // data_headers.result_code != 1 here so base.Parse() short-circuits before the
+        // subclass Parse runs.
+        if (info is null) return Ok(new { });
         return Ok(info);
     }
 
@@ -35,6 +40,11 @@ public class BattlePassController : SVSimController
         if (!TryGetViewerId(out long viewerId)) return Unauthorized();
 
         var list = await _battlePass.GetItemListAsync(viewerId, ct);
+        // TODO(off-season-crash): Empty {} body crashes BattlePassPurchaseInfoTask.Parse() on the
+        // client (unconditional jsonData["premium_pass_description"] access). Unreachable in
+        // practice — season 23 outlasts the Cygames shutdown. If a season-24+ ever lands, set
+        // data_headers.result_code != 1 here so base.Parse() short-circuits before the
+        // subclass Parse runs.
         if (list is null) return Ok(new { });
         return Ok(list);
     }

SVSim.EmulatedEntrypoint/Models/Dtos/BattlePass/BattlePassItemListResponse.cs

@@ -16,7 +16,8 @@ public class BattlePassItemListResponse
 
     [JsonPropertyName("sales_period_info")]
     [Key("sales_period_info")]
-    public BattlePassSalesPeriodInfoDto? SalesPeriodInfo { get; set; }
+    [JsonIgnore(Condition = JsonIgnoreCondition.Never)]
+    public BattlePassSalesPeriodInfoDto SalesPeriodInfo { get; set; } = new();
 
     [JsonPropertyName("products")]
     [Key("products")]

SVSim.EmulatedEntrypoint/Services/BattlePassService.cs

@@ -203,7 +203,7 @@ public sealed class BattlePassService : IBattlePassService
         // append the post-deduction total so the client gets the correct final balance.
         postState.RemoveAll(r => r.RewardType == (int)UserGoodsType.Crystal);
         postState.Add(new GrantedReward(
-            (int)UserGoodsType.Crystal, 0, checked((int)viewer.Currency.Crystals)));
+            (int)UserGoodsType.Crystal, 0, (int)viewer.Currency.Crystals));
 
         return new BattlePassBuyOutcome(1, achieved, postState);
     }