fix(studio): Task 4 — bind PaperdollController + wire empty-slot sprites

FixtureProvider.Populate for 0x21000023 was binding only
InventoryController and omitting PaperdollController, so the
~21 equip slots rendered empty even though sample equipped items
existed in the table.  Also, the three per-list empty-slot
sprites were not being resolved from the dat (contentsEmpty /
sideBagEmpty / mainPackEmpty all defaulted to 0), so the slot cells
had no background art.

Fixes:
- FixtureProvider.Populate gains a DatCollection dats param
  (mirrors the GameWindow.OnLoad lookup at line 2233-2235).
  The 0x21000023 case now resolves all three empty sprites via
  ItemListCellTemplate.ResolveEmptySprite and passes them to
  InventoryController.Bind.
- PaperdollController.Bind is now called after InventoryController
  in the same 0x21000023 case, matching GameWindow:2257-2265
  (same layout subtree, contentsEmpty as the equip-slot placeholder,
  sendWield: null since there is no live session in the studio).
- StudioWindow.OnLoad passes _dats! to the updated Populate signature.

SampleData.AddEquipped was already correct: MoveItem(guid, PlayerGuid,
-1, equipMask) at ClientObjectTable.cs:134 sets
CurrentlyEquippedLocation = newEquipLocation and calls Reindex which
places the item in _containerIndex[PlayerGuid].  No SampleData change
needed.

Tests: 2 new assertions in FixtureProviderTests —
  sideBags_matchInventoryControllerFilter (Type.HasFlag(Container)
  || ItemsCapacity > 0 filter must match both bags) and
  equippedItems_retainLocationAndAreInContents (equipped items have
  CurrentlyEquippedLocation != None AND appear in GetContents so the
  paperdoll controller can find them).  604 pass / 2 skip / 0 fail.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/AcDream.App.Tests/Studio/FixtureProviderTests.cs

@@ -102,4 +102,59 @@ public class FixtureProviderTests
         Assert.True(bagCount >= 2,
             $"Expected >= 2 side-bag containers in player pack; got {bagCount}");
     }
+
+    /// <summary>
+    /// Side bags must match the InventoryController filter: ItemType.Container OR ItemsCapacity &gt; 0.
+    /// This ensures they appear in the side-bag column even if the exact Type flag changes.
+    /// </summary>
+    [Fact]
+    public void SampleTable_sideBags_matchInventoryControllerFilter()
+    {
+        var t = SampleData.BuildObjectTable();
+
+        int bagCount = 0;
+        foreach (var guid in t.GetContents(SampleData.PlayerGuid))
+        {
+            var obj = t.Get(guid);
+            if (obj is null) continue;
+            // InventoryController.Populate line ~203: Type.HasFlag(Container) OR ItemsCapacity > 0
+            bool isBag = obj.Type.HasFlag(ItemType.Container) || obj.ItemsCapacity > 0;
+            if (isBag) bagCount++;
+        }
+
+        Assert.True(bagCount >= 2,
+            $"Expected >= 2 items matching the side-bag filter; got {bagCount}");
+    }
+
+    /// <summary>
+    /// Equipped items must BOTH (a) retain CurrentlyEquippedLocation != None after
+    /// seeding AND (b) appear in GetContents(PlayerGuid) so PaperdollController.Populate
+    /// can find them.  These are the two conditions PaperdollController checks on every
+    /// equipped item (PaperdollController.Populate: ContainerId == playerGuid AND
+    /// CurrentlyEquippedLocation != None).
+    /// </summary>
+    [Fact]
+    public void SampleTable_equippedItems_retainLocationAndAreInContents()
+    {
+        var t = SampleData.BuildObjectTable();
+        var contents = new System.Collections.Generic.HashSet<uint>(t.GetContents(SampleData.PlayerGuid));
+
+        int equippedCount = 0;
+        foreach (var obj in t.Objects)
+        {
+            if (obj.CurrentlyEquippedLocation == EquipMask.None) continue;
+            equippedCount++;
+
+            // Must appear in GetContents so the controller can pick them up.
+            Assert.True(contents.Contains(obj.ObjectId),
+                $"Equipped item 0x{obj.ObjectId:X8} ('{obj.Name}', loc={obj.CurrentlyEquippedLocation}) " +
+                $"is NOT in GetContents(PlayerGuid). PaperdollController will miss it.");
+
+            // The equip location must survive the MoveItem call.
+            Assert.NotEqual(EquipMask.None, obj.CurrentlyEquippedLocation);
+        }
+
+        Assert.True(equippedCount >= 3,
+            $"Expected >= 3 equipped items in sample table; got {equippedCount}");
+    }
 }