feat(net): InventoryActions — stack merge/split + give + shortcut + poi recall

Outbound GameActions for the inventory/drag-drop UI and quickbar:

- StackableMerge (0x0054): u32 mergeFrom, u32 mergeTo, u32 amount.
  Combine two same-type stacks.
- StackableSplitToContainer (0x0055): u32 stack, u32 container,
  u32 placement, u32 amount. Drag a portion of a stack into a pack slot.
- StackableSplitTo3D (0x0056): u32 stack, u32 amount. Drop N items to
  the ground.
- StackableSplitToWield (0x019B): u32 stack, u32 equipLoc, u32 amount.
  Split off and immediately equip (e.g. split an arrow stack to
  missile-ammo slot).
- GiveObjectRequest (0x00CD): u32 target, u32 item, u32 amount. Give to
  NPC / other player.
- AddShortcut (0x019C): u32 slot, u32 objectType, u32 targetId.
  Pin an item / spell to a quickbar.
- RemoveShortcut (0x019D): u32 slot. Unpin.
- TeleToPoi (0x00B1): u32 poiId. Quest-driven recall.

Tests (8 new): byte-exact encoding of each action, including size
assertions so breaking changes surface immediately.

Build green, 190 Core.Net tests pass (up from 182).

Ref: r08 §3 inventory / shortcut rows.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/AcDream.Core.Net.Tests/Messages/InventoryActionsTests.cs

@@ -0,0 +1,109 @@
+using System;
+using System.Buffers.Binary;
+using AcDream.Core.Net.Messages;
+using Xunit;
+
+namespace AcDream.Core.Net.Tests.Messages;
+
+public sealed class InventoryActionsTests
+{
+    [Fact]
+    public void BuildStackableMerge_CarriesBothGuidsAndAmount()
+    {
+        byte[] body = InventoryActions.BuildStackableMerge(
+            seq: 1, mergeFromGuid: 0xAA, mergeToGuid: 0xBB, amount: 5);
+
+        Assert.Equal(24, body.Length);
+        Assert.Equal(InventoryActions.StackableMergeOpcode,
+            BinaryPrimitives.ReadUInt32LittleEndian(body.AsSpan(8)));
+        Assert.Equal(0xAAu,
+            BinaryPrimitives.ReadUInt32LittleEndian(body.AsSpan(12)));
+        Assert.Equal(0xBBu,
+            BinaryPrimitives.ReadUInt32LittleEndian(body.AsSpan(16)));
+        Assert.Equal(5u,
+            BinaryPrimitives.ReadUInt32LittleEndian(body.AsSpan(20)));
+    }
+
+    [Fact]
+    public void BuildStackableSplitToContainer_FourFields()
+    {
+        byte[] body = InventoryActions.BuildStackableSplitToContainer(
+            seq: 1, stackGuid: 0xAA, containerGuid: 0xBB, placement: 3, amount: 10);
+
+        Assert.Equal(28, body.Length);
+        Assert.Equal(InventoryActions.StackableSplitToContainerOpcode,
+            BinaryPrimitives.ReadUInt32LittleEndian(body.AsSpan(8)));
+        Assert.Equal(3u,
+            BinaryPrimitives.ReadUInt32LittleEndian(body.AsSpan(20)));
+        Assert.Equal(10u,
+            BinaryPrimitives.ReadUInt32LittleEndian(body.AsSpan(24)));
+    }
+
+    [Fact]
+    public void BuildStackableSplitTo3D_TwoFields()
+    {
+        byte[] body = InventoryActions.BuildStackableSplitTo3D(
+            seq: 1, stackGuid: 0xAA, amount: 3);
+        Assert.Equal(20, body.Length);
+        Assert.Equal(InventoryActions.StackableSplitTo3DOpcode,
+            BinaryPrimitives.ReadUInt32LittleEndian(body.AsSpan(8)));
+    }
+
+    [Fact]
+    public void BuildStackableSplitToWield_HasEquipLocation()
+    {
+        byte[] body = InventoryActions.BuildStackableSplitToWield(
+            seq: 1, stackGuid: 0xAA, equipLocation: 0x00400000, amount: 1);
+        Assert.Equal(0x00400000u,
+            BinaryPrimitives.ReadUInt32LittleEndian(body.AsSpan(16)));
+    }
+
+    [Fact]
+    public void BuildGiveObjectRequest_TargetItemAmount()
+    {
+        byte[] body = InventoryActions.BuildGiveObjectRequest(
+            seq: 1, targetGuid: 0xAA, itemGuid: 0xBB, amount: 2);
+        Assert.Equal(InventoryActions.GiveObjectRequestOpcode,
+            BinaryPrimitives.ReadUInt32LittleEndian(body.AsSpan(8)));
+        Assert.Equal(0xAAu,
+            BinaryPrimitives.ReadUInt32LittleEndian(body.AsSpan(12)));
+        Assert.Equal(0xBBu,
+            BinaryPrimitives.ReadUInt32LittleEndian(body.AsSpan(16)));
+        Assert.Equal(2u,
+            BinaryPrimitives.ReadUInt32LittleEndian(body.AsSpan(20)));
+    }
+
+    [Fact]
+    public void BuildAddShortcut_ThreeFields()
+    {
+        byte[] body = InventoryActions.BuildAddShortcut(
+            seq: 1, slotIndex: 0, objectType: 1, targetId: 0x3E1);
+        Assert.Equal(InventoryActions.AddShortcutOpcode,
+            BinaryPrimitives.ReadUInt32LittleEndian(body.AsSpan(8)));
+        Assert.Equal(0u,
+            BinaryPrimitives.ReadUInt32LittleEndian(body.AsSpan(12)));
+        Assert.Equal(1u,
+            BinaryPrimitives.ReadUInt32LittleEndian(body.AsSpan(16)));
+        Assert.Equal(0x3E1u,
+            BinaryPrimitives.ReadUInt32LittleEndian(body.AsSpan(20)));
+    }
+
+    [Fact]
+    public void BuildRemoveShortcut_HasSlotOnly()
+    {
+        byte[] body = InventoryActions.BuildRemoveShortcut(seq: 1, slotIndex: 5);
+        Assert.Equal(16, body.Length);
+        Assert.Equal(5u,
+            BinaryPrimitives.ReadUInt32LittleEndian(body.AsSpan(12)));
+    }
+
+    [Fact]
+    public void BuildTeleToPoi_SimpleIdPayload()
+    {
+        byte[] body = InventoryActions.BuildTeleToPoi(seq: 1, poiId: 42);
+        Assert.Equal(InventoryActions.TeleToPoiOpcode,
+            BinaryPrimitives.ReadUInt32LittleEndian(body.AsSpan(8)));
+        Assert.Equal(42u,
+            BinaryPrimitives.ReadUInt32LittleEndian(body.AsSpan(12)));
+    }
+}