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>

tests/AcDream.App.Tests/UI/UiScrollablePanelTests.cs

@@ -0,0 +1,39 @@
+using AcDream.App.UI;
+
+namespace AcDream.App.Tests.UI;
+
+public sealed class UiScrollablePanelTests
+{
+    [Fact]
+    public void LayoutScrollableChildren_ClipsRowsOutsideViewport()
+    {
+        var panel = new UiScrollablePanel { Width = 100, Height = 40, LineHeight = 20 };
+        for (int i = 0; i < 4; i++)
+            panel.AddChild(new UiPanel { Top = i * 20, Width = 100, Height = 20 });
+
+        panel.LayoutScrollableChildren();
+        Assert.True(panel.Children[0].Visible);
+        Assert.True(panel.Children[1].Visible);
+        Assert.False(panel.Children[2].Visible);
+
+        panel.Scroll.SetScrollY(20);
+        panel.LayoutScrollableChildren();
+        Assert.False(panel.Children[0].Visible);
+        Assert.True(panel.Children[1].Visible);
+        Assert.True(panel.Children[2].Visible);
+    }
+
+    [Fact]
+    public void ScrollEvent_MovesByLineHeight()
+    {
+        var panel = new UiScrollablePanel { Width = 100, Height = 40, LineHeight = 20 };
+        for (int i = 0; i < 4; i++)
+            panel.AddChild(new UiPanel { Top = i * 20, Width = 100, Height = 20 });
+        panel.LayoutScrollableChildren();
+
+        var e = new UiEvent(0u, panel, UiEventType.Scroll, Data0: -1);
+        Assert.True(panel.OnEvent(in e));
+
+        Assert.Equal(20, panel.Scroll.ScrollY);
+    }
+}