AX Agent popup 시각 언어 통일 및 선택 surface 후속 정리

- 공통 popup factory가 surface visual helper를 사용하도록 정리
- worktree 선택과 권한 모드 row의 border/hover/selected 규칙을 같은 visual language로 통일
- README와 DEVELOPMENT 문서에 2026-04-06 11:27 (KST) 기준 popup polish 누적 범위 반영
- dotnet build 검증 경고 0, 오류 0 확인

src/AxCopilot/Views/ChatWindow.PopupPresentation.cs

@@ -19,27 +19,8 @@ public partial class ChatWindow
     {
         _sharedContextPopup?.SetCurrentValue(Popup.IsOpenProperty, false);
 
-        var bg = TryFindResource("LauncherBackground") as Brush ?? Brushes.White;
-        var border = TryFindResource("BorderColor") as Brush ?? Brushes.Gray;
         var panel = new StackPanel { Margin = new Thickness(2) };
-        var container = new Border
-        {
-            Background = bg,
-            BorderBrush = border,
-            BorderThickness = new Thickness(1),
-            CornerRadius = new CornerRadius(10),
-            Padding = new Thickness(6),
-            MinWidth = minWidth,
-            Child = panel,
-            Effect = new System.Windows.Media.Effects.DropShadowEffect
-            {
-                BlurRadius = 16,
-                ShadowDepth = 3,
-                Opacity = 0.18,
-                Color = Colors.Black,
-                Direction = 270,
-            },
-        };
+        var container = CreateSurfacePopupContainer(panel, minWidth, new Thickness(6));
 
         var popup = new Popup
         {
@@ -64,40 +45,13 @@ public partial class ChatWindow
         Brush hoverBrush,
         Action action)
     {
-        var sp = new StackPanel { Orientation = Orientation.Horizontal };
-        sp.Children.Add(new TextBlock
-        {
-            Text = icon,
-            FontFamily = new FontFamily("Segoe MDL2 Assets"),
-            FontSize = 12.5,
-            Foreground = iconBrush,
-            VerticalAlignment = VerticalAlignment.Center,
-            Margin = new Thickness(0, 0, 9, 0),
-        });
-        sp.Children.Add(new TextBlock
-        {
-            Text = label,
-            FontSize = 12.5,
-            Foreground = labelBrush,
-            VerticalAlignment = VerticalAlignment.Center,
-        });
-
-        var item = new Border
-        {
-            Child = sp,
-            Background = Brushes.Transparent,
-            CornerRadius = new CornerRadius(8),
-            Cursor = Cursors.Hand,
-            Padding = new Thickness(10, 7, 12, 7),
-            Margin = new Thickness(0, 1, 0, 1),
-        };
-        item.MouseEnter += (s, _) => { if (s is Border b) b.Background = hoverBrush; };
-        item.MouseLeave += (s, _) => { if (s is Border b) b.Background = Brushes.Transparent; };
-        item.MouseLeftButtonUp += (_, _) =>
+        var item = CreateSurfacePopupMenuItem(icon, iconBrush, label, () =>
         {
             popup.SetCurrentValue(Popup.IsOpenProperty, false);
             action();
-        };
+        }, labelBrush);
+        item.MouseEnter += (s, _) => { if (s is Border b) b.Background = hoverBrush; };
+        item.MouseLeave += (s, _) => { if (s is Border b) b.Background = Brushes.Transparent; };
 
         return item;
     }