feat(D.2b): ClientObjectTable.ReplaceContents — authoritative full-replace for ViewContents

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/AcDream.Core/Items/ClientObjectTable.cs

@@ -314,6 +314,52 @@ public sealed class ClientObjectTable
         _containerIndex.TryGetValue(containerId, out var l)
             ? l.ToArray() : System.Array.Empty<uint>();
 
+    /// <summary>
+    /// Replace a container's entire membership with <paramref name="guids"/> (in order) — the
+    /// authoritative full snapshot the server sends in ViewContents (0x0196) when you open a
+    /// container. Members no longer present are detached (ContainerId → 0); new members are
+    /// recorded with ContainerSlot = list index. ACE writes ViewContents entries
+    /// OrderBy(PlacementPosition) with NO explicit slot field (GameEventViewContents.cs), so the
+    /// list order IS the slot order. Fires ObjectAdded/ObjectMoved so bound UI repaints.
+    /// Retail consumer: ClientUISystem::OnViewContents.
+    /// </summary>
+    public void ReplaceContents(uint containerId, IReadOnlyList<uint> guids)
+    {
+        ArgumentNullException.ThrowIfNull(guids);
+        if (containerId == 0) return;
+
+        var keep = new HashSet<uint>(guids);
+
+        // Detach prior members no longer present (they left the container server-side). GetContents
+        // returns a snapshot, so mutating the index inside the loop is safe.
+        foreach (var old in GetContents(containerId))
+        {
+            if (keep.Contains(old)) continue;
+            if (!_objects.TryGetValue(old, out var o) || o.ContainerId != containerId) continue;
+            o.ContainerId = 0;
+            Reindex(o, containerId);
+            ObjectMoved?.Invoke(o, containerId, 0);
+        }
+
+        // Record new members in order; ContainerSlot = index reconstructs the server PlacementPosition.
+        for (int i = 0; i < guids.Count; i++)
+        {
+            uint g = guids[i];
+            bool existed = _objects.TryGetValue(g, out var obj);
+            if (!existed || obj is null)
+            {
+                obj = new ClientObject { ObjectId = g };
+                _objects[g] = obj;
+            }
+            uint oldContainer = obj.ContainerId;
+            obj.ContainerId = containerId;
+            obj.ContainerSlot = i;
+            Reindex(obj, oldContainer);
+            if (!existed) ObjectAdded?.Invoke(obj);
+            else ObjectMoved?.Invoke(obj, oldContainer, containerId);
+        }
+    }
+
     /// <summary>
     /// Σ Burden over every object carried by <paramref name="ownerGuid"/>: items
     /// whose container chain roots at the owner (pack + side-bag contents, retail