feat(ui): D.2b-B — InventoryController bind + grid population (loose/side-bag partition)

Task 4: InventoryController.Bind + Populate: find-by-id bind for the 7 inventory
element ids, configure grid (6 cols x 32px) + container list, partition
GetContents(player) into loose items (contentsGrid) vs side bags (containerList),
populate main-pack cell in topContainer, subscribe ObjectAdded/Moved/Removed/Updated
for live rebuilds. Handles both Ingest-indexed (production) and AddOrUpdate-direct
(test) paths via fallback scan.

Task 5: burden meter (vertical UiMeter, FillFromBottom=true) + RefreshBurden port
of CACQualities::InqLoad (decomp 0x0058f130) → gmBackpackUI::SetLoadLevel
(0x004a6ea0): EncumbranceCapacity/LoadRatio/LoadToFill/LoadToPercent. Three
AttachCaption overlays (Burden, Contents of Backpack, %text). 5 tests all green.

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

tests/AcDream.App.Tests/UI/Layout/InventoryControllerTests.cs

@@ -0,0 +1,138 @@
+using System.Collections.Generic;
+using AcDream.App.UI;
+using AcDream.App.UI.Layout;
+using AcDream.Core.Items;
+using Xunit;
+
+namespace AcDream.App.Tests.UI.Layout;
+
+public class InventoryControllerTests
+{
+    private const uint Player = 0x50000001u;
+
+    // UiElement is abstract — a concrete, parameterless stand-in for the root + caption hosts
+    // (the real captions are Type-0 → UiDatElement; in tests we only need a host that holds children).
+    private sealed class TestElement : UiElement { }
+
+    // Element ids (spec §1).
+    private const uint ContentsGrid    = 0x100001C6u;
+    private const uint ContainerList   = 0x100001CAu;
+    private const uint TopContainer    = 0x100001C9u;
+    private const uint BurdenMeter     = 0x100001D9u;
+    private const uint BurdenText      = 0x100001D8u;
+    private const uint BurdenCaption   = 0x100001D7u;
+    private const uint ContentsCaption = 0x100001C5u;
+
+    private static (ImportedLayout layout, UiItemList grid, UiItemList containers,
+                    UiItemList top, UiMeter meter, UiElement burdenText,
+                    UiElement burdenCap, UiElement contentsCap) BuildLayout()
+    {
+        var grid        = new UiItemList { Width = 192, Height = 96 };
+        var containers  = new UiItemList { Width = 36,  Height = 252 };
+        var top         = new UiItemList { Width = 36,  Height = 36 };
+        var meter       = new UiMeter    { Width = 11,  Height = 58 };
+        var burdenText  = new TestElement { Width = 36,  Height = 15 };
+        var burdenCap   = new TestElement { Width = 36,  Height = 15 };
+        var contentsCap = new TestElement { Width = 192, Height = 15 };
+        var root        = new TestElement { Width = 300, Height = 362 };
+        root.AddChild(grid); root.AddChild(containers); root.AddChild(top);
+        root.AddChild(meter); root.AddChild(burdenText); root.AddChild(burdenCap);
+        root.AddChild(contentsCap);
+        var byId = new Dictionary<uint, UiElement>
+        {
+            [ContentsGrid]    = grid, [ContainerList] = containers, [TopContainer] = top,
+            [BurdenMeter]     = meter, [BurdenText] = burdenText, [BurdenCaption] = burdenCap,
+            [ContentsCaption] = contentsCap,
+        };
+        return (new ImportedLayout(root, byId), grid, containers, top, meter,
+                burdenText, burdenCap, contentsCap);
+    }
+
+    private static InventoryController Bind(ImportedLayout layout, ClientObjectTable objects,
+        int? strength = 100)
+        => InventoryController.Bind(layout, objects, () => Player,
+            iconIds: (_, _, _, _, _) => 0u,        // no real GL upload in tests
+            strength: () => strength, datFont: null);
+
+    [Fact]
+    public void Populate_fills_contents_grid_with_loose_items_only()
+    {
+        var (layout, grid, containers, _, _, _, _, _) = BuildLayout();
+        var objects = new ClientObjectTable();
+        objects.AddOrUpdate(new ClientObject { ObjectId = 0xA, ContainerId = Player,
+            ContainerSlot = 0, Burden = 10 });                                   // loose
+        objects.AddOrUpdate(new ClientObject { ObjectId = 0xB, ContainerId = Player,
+            ContainerSlot = 1, Burden = 20 });                                   // loose
+        objects.AddOrUpdate(new ClientObject { ObjectId = 0xC, ContainerId = Player,
+            ContainerSlot = 2, Type = ItemType.Container });                     // side bag
+
+        Bind(layout, objects);
+
+        Assert.Equal(2, grid.GetNumUIItems());          // 2 loose
+        Assert.Equal(0xAu, grid.GetItem(0)!.ItemId);
+        Assert.Equal(0xBu, grid.GetItem(1)!.ItemId);
+        Assert.Equal(1, containers.GetNumUIItems());     // 1 side bag
+        Assert.Equal(0xCu, containers.GetItem(0)!.ItemId);
+    }
+
+    [Fact]
+    public void Grid_is_six_columns_thirtytwo_px()
+    {
+        var (layout, grid, _, _, _, _, _, _) = BuildLayout();
+        Bind(layout, new ClientObjectTable());
+        Assert.Equal(6, grid.Columns);
+        Assert.Equal(32f, grid.CellWidth);
+        Assert.Equal(32f, grid.CellHeight);
+    }
+
+    [Fact]
+    public void ObjectAdded_for_player_item_rebuilds_grid()
+    {
+        var (layout, grid, _, _, _, _, _, _) = BuildLayout();
+        var objects = new ClientObjectTable();
+        Bind(layout, objects);
+        Assert.Equal(0, grid.GetNumUIItems());
+
+        objects.Ingest(new WeenieData(0xA, "Sword", ItemType.MeleeWeapon, 1, 0, 0, 0, 0,
+            null, null, null, 5, Player, null, null, null, null, null, null, null, null, null));
+
+        Assert.Equal(1, grid.GetNumUIItems());
+        Assert.Equal(0xAu, grid.GetItem(0)!.ItemId);
+    }
+
+    [Fact]
+    public void Burden_meter_fill_and_percent_from_load()
+    {
+        var (layout, _, _, _, meter, burdenText, _, _) = BuildLayout();
+        var objects = new ClientObjectTable();
+        // Str 100 → capacity 15000. Carried 7500 → load 0.5 → fill 0.1667, "50%".
+        objects.AddOrUpdate(new ClientObject { ObjectId = 0xA, ContainerId = Player, Burden = 7500 });
+        Bind(layout, objects, strength: 100);
+
+        Assert.Equal(0.16667f, meter.Fill() ?? -1f, 3);
+        Assert.True(meter.Vertical);
+        // The % text caption child reads "50%".
+        Assert.Contains("50%", CaptionText(burdenText));
+    }
+
+    [Fact]
+    public void Captions_render_known_strings()
+    {
+        var (layout, _, _, _, _, _, burdenCap, contentsCap) = BuildLayout();
+        Bind(layout, new ClientObjectTable());
+        Assert.Contains("Burden", CaptionText(burdenCap));
+        Assert.Contains("Contents of Backpack", CaptionText(contentsCap));
+    }
+
+    // Reads the text of the UiText caption child attached by the controller.
+    private static string CaptionText(UiElement host)
+    {
+        foreach (var c in host.Children)
+            if (c is UiText t)
+            {
+                var lines = t.LinesProvider();
+                if (lines.Count > 0) return lines[0].Text;
+            }
+        return "";
+    }
+}