test(inventory): wire-shape regression for spend+grant+cascade

Serializes result.RewardList with snake_case+WhenWritingNull options and
asserts the three entries come out in expected first-touch order:
Crystal post-state (500), Card post-state count (3), Sleeve cascade (1).
Also verifies snake_case key names are actually emitted.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

SVSim.UnitTests/Wire/InventoryRewardListWireShape.cs

@@ -0,0 +1,71 @@
+using System.Text.Json;
+using System.Text.Json.Serialization;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.DependencyInjection;
+using SVSim.Database;
+using SVSim.Database.Enums;
+using SVSim.Database.Models;
+using SVSim.Database.Services;
+using SVSim.Database.Services.Inventory;
+using SVSim.UnitTests.Infrastructure;
+
+namespace SVSim.UnitTests.Wire;
+
+public class InventoryRewardListWireShape
+{
+    [Test]
+    public async Task Spend_crystal_plus_grant_card_with_cascade_matches_fixture()
+    {
+        using var factory = new SVSimTestFactory();
+        long viewerId = await factory.SeedViewerAsync();
+        long cardId = await factory.SeedCardAsync();
+        using var scope = factory.Services.CreateScope();
+        var ctx = scope.ServiceProvider.GetRequiredService<SVSimDbContext>();
+        var v = await ctx.Viewers.FirstAsync(x => x.Id == viewerId);
+        v.Currency.Crystals = 1000;
+        const int sleeveId = 2_000_040_000;
+        ctx.Sleeves.Add(new SleeveEntry { Id = sleeveId });
+        ctx.CardCosmeticRewards.Add(new CardCosmeticReward { CardId = cardId, CosmeticId = sleeveId, Type = CosmeticType.Sleeve });
+        await ctx.SaveChangesAsync();
+
+        var inv = scope.ServiceProvider.GetRequiredService<IInventoryService>();
+        await using var tx = await inv.BeginAsync(viewerId);
+        await tx.TrySpendAsync(SpendCurrency.Crystal, 500);
+        await tx.GrantAsync(UserGoodsType.Card, cardId, 3);
+        var result = await tx.CommitAsync();
+
+        var opts = new JsonSerializerOptions
+        {
+            PropertyNamingPolicy = JsonNamingPolicy.SnakeCaseLower,
+            DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull,
+        };
+        var json = JsonSerializer.Serialize(result.RewardList, opts);
+
+        // Expected order: currency entries in first-touch order, then non-currency in first-touch order.
+        // Crystal spend comes first (post-state 500), then Card grant (post-state count 3), then
+        // Sleeve cascade (always 1).
+        var doc = JsonDocument.Parse(json);
+        var arr = doc.RootElement.EnumerateArray().ToList();
+        Assert.That(arr, Has.Count.EqualTo(3), $"Expected 3 reward entries, got {arr.Count}. JSON: {json}");
+
+        Assert.That(arr[0].GetProperty("reward_type").GetInt32(), Is.EqualTo((int)UserGoodsType.Crystal),
+            "First entry should be Crystal (spend post-state)");
+        Assert.That(arr[0].GetProperty("reward_num").GetInt32(), Is.EqualTo(500),
+            "Crystal post-state after spending 500 from 1000 should be 500");
+
+        Assert.That(arr[1].GetProperty("reward_type").GetInt32(), Is.EqualTo((int)UserGoodsType.Card),
+            "Second entry should be Card");
+        Assert.That(arr[1].GetProperty("reward_num").GetInt32(), Is.EqualTo(3),
+            "Card post-state count for fresh grant of 3 should be 3");
+
+        Assert.That(arr[2].GetProperty("reward_type").GetInt32(), Is.EqualTo((int)UserGoodsType.Sleeve),
+            "Third entry should be Sleeve (cascade from card grant)");
+        Assert.That(arr[2].GetProperty("reward_id").GetInt32(), Is.EqualTo(sleeveId),
+            "Sleeve reward_id should match the seeded sleeve");
+
+        // Verify snake_case keys are present (not PascalCase)
+        Assert.That(arr[0].TryGetProperty("reward_type", out _), Is.True, "Key must be reward_type not RewardType");
+        Assert.That(arr[0].TryGetProperty("reward_id", out _), Is.True, "Key must be reward_id not RewardId");
+        Assert.That(arr[0].TryGetProperty("reward_num", out _), Is.True, "Key must be reward_num not RewardNum");
+    }
+}