feat(items): port retail external-container looting

Add the ClientUISystem ground-object lifecycle, authoritative root and nested ViewContents projections, replacement and close semantics, and the DAT-authored gmExternalContainerUI strip for chests and corpses.

Route double-click loot and full or partial drag transfers through the shared retail item policy without optimistic external ownership. Remove the incorrect NoLongerViewingContents behavior from owned side packs and retire AP-106/#196.

Release build succeeds and all 5,875 tests pass with five intentional skips.

Co-authored-by: OpenAI Codex <codex@openai.com>

tests/AcDream.App.Tests/UI/ItemInteractionControllerTests.cs

@@ -19,6 +19,8 @@ public sealed class ItemInteractionControllerTests
         public readonly List<(uint Source, uint Target)> UseWithTarget = new();
         public readonly List<(uint Item, uint Mask)> Wields = new();
         public readonly List<(uint Item, uint Container, int Placement)> Puts = new();
+        public readonly List<(uint Item, uint Container, uint Placement, uint Amount)> SplitPuts = new();
+        public readonly List<uint> ExternalRequests = new();
         public readonly List<uint> Drops = new();
         public readonly List<(uint Item, uint Amount)> SplitDrops = new();
         public readonly List<(uint Target, uint Item, uint Amount)> Gives = new();
@@ -28,6 +30,7 @@ public sealed class ItemInteractionControllerTests
         public uint SelectedObject;
         public bool NonCombatMode;
         public bool DragOnPlayerOpensSecureTrade = true;
+        public uint GroundObject;
         public long Now = 1_000;
 
         public Harness()
@@ -61,11 +64,19 @@ public sealed class ItemInteractionControllerTests
                 selectedObjectId: () => SelectedObject,
                 stackSplitQuantity: SplitQuantity,
                 inNonCombatMode: () => NonCombatMode,
+                groundObjectId: () => GroundObject,
                 sendPutItemInContainer: (item, container, placement) =>
                     Puts.Add((item, container, placement)),
                 sendGive: (target, item, amount) => Gives.Add((target, item, amount)),
                 dragOnPlayerOpensSecureTrade: () => DragOnPlayerOpensSecureTrade,
-                systemMessage: SystemMessages.Add);
+                systemMessage: SystemMessages.Add,
+                sendSplitToContainer: (item, container, placement, amount) =>
+                    SplitPuts.Add((item, container, placement, amount)),
+                requestExternalContainer: id =>
+                {
+                    GroundObject = id;
+                    ExternalRequests.Add(id);
+                });
         }
 
         public ItemInteractionController Controller { get; }
@@ -103,6 +114,51 @@ public sealed class ItemInteractionControllerTests
         Assert.Empty(h.UseWithTarget);
     }
 
+    [Fact]
+    public void ExternalContainerUse_RequestsGroundObjectAndSendsUse()
+    {
+        var h = new Harness();
+        const uint chest = 0x70000001u;
+        h.Objects.AddOrUpdate(new ClientObject
+        {
+            ObjectId = chest,
+            Type = ItemType.Container,
+            ItemsCapacity = 24,
+            Useability = ItemUseability.Remote,
+        });
+
+        Assert.True(h.Controller.ActivateItem(chest));
+
+        Assert.Equal(new uint[] { chest }, h.Uses);
+        Assert.Equal(new uint[] { chest }, h.ExternalRequests);
+        Assert.Equal(chest, h.GroundObject);
+    }
+
+    [Fact]
+    public void DropOwnedItemOnOpenExternalContainer_SendsPutWithoutOptimisticMove()
+    {
+        var h = new Harness();
+        const uint itemId = 0x50000A33u;
+        const uint chest = 0x70000001u;
+        ClientObject item = h.AddContained(itemId);
+        h.Objects.AddOrUpdate(new ClientObject
+        {
+            ObjectId = chest,
+            Type = ItemType.Container,
+            ItemsCapacity = 24,
+            PublicWeenieBitfield = (uint)PublicWeenieFlags.Openable,
+        });
+        h.GroundObject = chest;
+        var cell = new UiItemSlot();
+        cell.SetItem(itemId, 0u);
+        var payload = new ItemDragPayload(itemId, ItemDragSource.Inventory, 0, cell);
+
+        Assert.True(h.Controller.PlaceIn3D(payload, chest));
+
+        Assert.Equal(new[] { (itemId, chest, 0) }, h.Puts);
+        Assert.Equal(Pack, item.ContainerId);
+    }
+
     [Fact]
     public void PrimaryClickRouter_distinguishesInactiveSuccessAndConsumedRejection()
     {