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/UiScrollablePanel.cs

@@ -0,0 +1,109 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Numerics;
+
+namespace AcDream.App.UI;
+
+/// <summary>
+/// Simple vertical viewport for controller-built row lists. It shares the same
+/// pixel scroll model as chat text and item grids, and clips whole rows because
+/// the UI renderer does not have a scissor stack yet.
+/// </summary>
+public sealed class UiScrollablePanel : UiPanel
+{
+    private readonly Dictionary<UiElement, float> _baseTops = new(ReferenceEqualityComparer.Instance);
+
+    public UiScrollable Scroll { get; } = new();
+
+    public int LineHeight { get; set; } = 16;
+
+    public int ContentHeight { get; private set; }
+
+    public UiScrollablePanel()
+    {
+        BackgroundColor = Vector4.Zero;
+        BorderColor = Vector4.Zero;
+    }
+
+    public override void AddChild(UiElement child)
+    {
+        base.AddChild(child);
+        Track(child);
+    }
+
+    public override bool RemoveChild(UiElement child)
+    {
+        bool removed = base.RemoveChild(child);
+        if (removed)
+        {
+            _baseTops.Remove(child);
+            RecomputeContentHeight();
+        }
+        return removed;
+    }
+
+    public void ClearContent()
+    {
+        foreach (var child in Children.ToArray())
+            RemoveChild(child);
+        _baseTops.Clear();
+        ContentHeight = 0;
+        Scroll.SetScrollY(0);
+    }
+
+    internal void LayoutScrollableChildren()
+    {
+        Scroll.LineHeight = Math.Max(1, LineHeight);
+        Scroll.ContentHeight = ContentHeight;
+        Scroll.ViewHeight = Math.Max(0, (int)MathF.Floor(Height));
+        Scroll.SetScrollY(Scroll.ScrollY);
+
+        foreach (var child in Children)
+        {
+            if (!_baseTops.TryGetValue(child, out float baseTop))
+                continue;
+
+            float top = baseTop - Scroll.ScrollY;
+            child.Top = top;
+            child.Visible = top >= -0.5f && top + child.Height <= Height + 0.5f;
+        }
+    }
+
+    public override bool OnEvent(in UiEvent e)
+    {
+        if (e.Type == UiEventType.Scroll)
+        {
+            Scroll.ScrollByLines(-e.Data0);
+            LayoutScrollableChildren();
+            return true;
+        }
+        return base.OnEvent(e);
+    }
+
+    protected override void OnDraw(UiRenderContext ctx)
+    {
+        LayoutScrollableChildren();
+        base.OnDraw(ctx);
+    }
+
+    private void Track(UiElement child)
+    {
+        child.Anchors = AnchorEdges.None;
+        _baseTops[child] = child.Top;
+        RecomputeContentHeight();
+    }
+
+    private void RecomputeContentHeight()
+    {
+        float bottom = 0f;
+        foreach (var child in Children)
+        {
+            if (!_baseTops.TryGetValue(child, out float top))
+                continue;
+            bottom = MathF.Max(bottom, top + child.Height);
+        }
+        ContentHeight = (int)MathF.Ceiling(bottom);
+        Scroll.SetScrollY(Scroll.ScrollY);
+    }
+}