fix(vendor): a shop listing with zero stock is unlimited

src/AcDream.Core.Net/GameEventWiring.cs

@@ -697,9 +697,13 @@ void NotifyOfEnchantmentRemoval(uint spellId)
             for (int i = 0; i < shopItems.Length; i++)
             {
                 VendorApproach.ItemProfile item = p.Value.Items[i];
+                // ACE sends a shop create-list row's authored stack size
+                // as-is, and world content authors many of them as 0 rather
+                // than -1. ACE never limits a create-list item, so any
+                // non-positive count means the vendor never runs out.
                 shopItems[i] = new VendorShopItem(
                     item.ItemGuid,
-                    item.StackSize,
+                    item.StackSize > 0 ? item.StackSize : VendorComponentFill.UnlimitedStock,
                     item.Desc.WeenieClassId,
                     item.Desc.Name,
                     item.Desc.ItemType,

tests/AcDream.Runtime.Tests/Gameplay/RuntimeVendorLifecycleTests.cs

@@ -65,6 +65,46 @@ public void ApproachVendorEvent_PopulatesVendorStateWithProfileAndItems()
         Assert.Equal(250, item.Value);
     }
 
+    [Fact]
+    public void ApproachVendorEvent_ZeroStockListing_IsUnlimited()
+    {
+        using GameRuntime runtime = Create();
+        VendorState vendor = runtime.InventoryOwner.Vendor;
+        using IDisposable wiring = Wire(vendor);
+
+        // ACE sends a shop create-list row's authored stack size as-is, and
+        // world content authors many of them as 0. ACE never limits a
+        // create-list item, so 0 carries the same meaning as -1.
+        Dispatch(BuildApproachVendorPayload(
+            vendorGuid: 0x40001000u,
+            categories: 0x42u,
+            minValue: 0u,
+            maxValue: 500u,
+            dealsMagic: false,
+            buyPrice: 0.8f,
+            sellPrice: 1.3f,
+            currencyWcid: 0u,
+            currencyAmount: 0u,
+            currencyName: "",
+            items:
+            [
+                new VendorItemFixture(
+                    ItemGuid: 0x50002000u, StackSize: 0, Name: "Iron Sword",
+                    WeenieClassId: 42u, RawIconId: 0x1234u,
+                    ItemType: (uint)ItemType.Weapon, Value: 250),
+                new VendorItemFixture(
+                    ItemGuid: 0x50002001u, StackSize: -1, Name: "Bread",
+                    WeenieClassId: 43u, RawIconId: 0x1235u,
+                    ItemType: (uint)ItemType.Food, Value: 5),
+                new VendorItemFixture(
+                    ItemGuid: 0x50002002u, StackSize: 3, Name: "Leather Cap",
+                    WeenieClassId: 44u, RawIconId: 0x1236u,
+                    ItemType: (uint)ItemType.Armor, Value: 40),
+            ]));
+
+        Assert.Equal([-1, -1, 3], vendor.Items.Select(i => i.StackSize));
+    }
+
     [Fact]
     public void SecondApproachVendorEventFromDifferentVendor_ReplacesTheSession()
     {