feat(ui): D.2b item interaction + retail cursors + live character sheet

Lands the codex-worktree D.2b stream plus the extraction the 2026-07-02
UI architecture review mandated before commit:

- ItemInteractionController: single owner of double-click use/equip/
  container-open, targeted-use mode (health kits), drag-out drop;
  toolbar shortcut drags don't drop the real item. ItemEquipRules for
  multi-slot (coat) coverage via equip masks.
- Cursor phase: CursorFeedbackController (semantic priority chain:
  drag > resize > window-move > target-mode > text) + RetailCursorCatalog
  (enums 0x27/0x28/0x29, hotspot 14,14; ClientUISystem::UpdateCursorState
  0x00564630) resolved through the portal EnumIDMap chain by
  RetailCursorResolver; RetailCursorManager applies dat cursor art to the
  OS cursor. Register row AP-72 covers the OS standard-cursor fallback.
- Character window goes live: CharacterSheetProvider owns sheet assembly,
  XP-curve/raise-cost math and the raise flow — extracted out of
  GameWindow per Code Structure Rule 1 instead of committing the ~430-line
  feature body there. Optimistic XP/credit debits go through eventful
  store APIs (new ClientObjectTable.UpdateInt64Property +
  LocalPlayerState.DebitIntProperty/DebitInt64Property) instead of raw
  property-dictionary writes; register row AP-73 covers the still-missing
  raise ledger (#163).
- RetailWindowFrame: the shared nine-slice window mount recipe; the
  character window uses it, remaining windows migrate via #164.
- Status-bar buttons toggle inventory/character windows; retail row-major
  backpack ordering; WorldSession.SendUseWithTarget + raise/train sends.

GameWindow shrinks 14,214 -> 13,877 lines despite the new features; the
sheet/raise logic is unit-tested in CharacterSheetProviderTests instead
of trapped in the god object. Build green; full suite 3,286 tests pass.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/AcDream.App/UI/UiItemList.cs

@@ -3,6 +3,16 @@ using System.Collections.Generic;
 
 namespace AcDream.App.UI;
 
+/// <summary>Cell order for a multi-column <see cref="UiItemList"/>.</summary>
+public enum UiItemListFlow
+{
+    /// <summary>Retail listbox bit 0 set: index advances across columns, then down rows.</summary>
+    RowMajor,
+
+    /// <summary>Retail listbox bit 0 clear: index advances down rows, then across columns.</summary>
+    ColumnMajor,
+}
+
 /// <summary>
 /// A container of item cells (port of retail UIElement_ItemList, class 0x10000031).
 /// Behavioral LEAF: it creates/owns its UiItemSlot children procedurally, so the
@@ -82,9 +92,16 @@ public sealed class UiItemList : UiElement
         LayoutCells();
     }
 
-    /// <summary>Grid columns (row-major). 1 = single column. Ignored in fill mode.</summary>
+    /// <summary>Grid columns. 1 = single column. Ignored in fill mode.</summary>
     public int Columns { get; set; } = 1;
 
+    /// <summary>
+    /// Multi-column list flow. Retail UIElement_ListBox::UpdateLayout uses bit 0 of
+    /// m_bitField: set = row-major, clear = column-major. Default preserves the
+    /// existing toolbar/grid behavior; panel controllers select retail-specific flow.
+    /// </summary>
+    public UiItemListFlow Flow { get; set; } = UiItemListFlow.RowMajor;
+
     /// <summary>Fixed cell width in grid mode. 0 = "fill the list" — the single cell sizes
     /// to the whole list (the toolbar single-slot legacy). Set &gt;0 (with CellHeight) for a grid.</summary>
     public float CellWidth { get; set; }
@@ -107,8 +124,25 @@ public sealed class UiItemList : UiElement
         return (col * cellW, row * cellH);
     }
 
+    /// <summary>
+    /// Pixel offset matching retail UIElement_ListBox::CalculateColumn/CalculateRow:
+    /// row-major when bit 0 is set, column-major when it is clear.
+    /// </summary>
+    internal static (float x, float y) CellOffset(
+        int index, int columns, int cellCount, UiItemListFlow flow, float cellW, float cellH)
+    {
+        int cols = columns < 1 ? 1 : columns;
+        if (flow == UiItemListFlow.ColumnMajor)
+        {
+            int rows = Math.Max(1, RowCount(cellCount, cols));
+            int col = index / rows, row = index % rows;
+            return (col * cellW, row * cellH);
+        }
+        return CellOffset(index, cols, cellW, cellH);
+    }
+
     /// <summary>Position every cell per the current mode: fill (CellWidth&lt;=0) sizes the single
-    /// cell to the list; grid (CellWidth&gt;0) tiles cells row-major, offset by the scroll position
+    /// cell to the list; grid (CellWidth&gt;0) tiles cells by <see cref="Flow"/>, offset by the scroll position
     /// with whole-row vertical clipping (cells fully outside the view are hidden).</summary>
     internal void LayoutCells()
     {
@@ -137,7 +171,7 @@ public sealed class UiItemList : UiElement
 
         for (int i = 0; i < _cells.Count; i++)
         {
-            var (x, baseY) = CellOffset(i, cols, CellWidth, CellHeight);
+            var (x, baseY) = CellOffset(i, cols, _cells.Count, Flow, CellWidth, CellHeight);
             float top = baseY - scrollY;
             var cell = _cells[i];
             cell.Left = x; cell.Top = top; cell.Width = CellWidth; cell.Height = CellHeight;