AX Agent 프리셋 카드 hover 깜빡임 완화

- 채팅과 코워크 프리셋 카드 설명 라벨을 Visibility 토글 대신 Opacity 전환으로 변경
- 카드 hover 중 설명 라벨 표시 때문에 레이아웃이 다시 잡히며 깜빡이던 현상 완화
- README와 DEVELOPMENT 문서에 2026-04-05 22:57 (KST) 기준 작업 이력 반영
- 검증: dotnet build src/AxCopilot/AxCopilot.csproj -c Release -v minimal -p:OutputPath=bin\verify\ -p:IntermediateOutputPath=obj\verify\ (경고 0 / 오류 0)

src/AxCopilot/Views/ChatWindow.xaml.cs

@@ -12426,7 +12426,6 @@ public partial class ChatWindow : Window
                     b.Background = hoverBackground;
                     b.BorderBrush = TryFindResource("AccentColor") as Brush ?? cardBorder;
                 }
-                hoverLabel.Visibility = Visibility.Visible;
                 hoverLabel.Opacity = 1;
             };
             card.MouseLeave += (s, _) =>
@@ -12436,7 +12435,7 @@ public partial class ChatWindow : Window
                     b.Background = normalBackground;
                     b.BorderBrush = cardBorder;
                 }
-                hoverLabel.Visibility = Visibility.Collapsed;
+                hoverLabel.Opacity = 0;
             };
         }
 
@@ -12508,7 +12507,8 @@ public partial class ChatWindow : Window
                 Margin = new Thickness(8, 0, 8, 6),
                 VerticalAlignment = VerticalAlignment.Bottom,
                 HorizontalAlignment = HorizontalAlignment.Stretch,
-                Visibility = Visibility.Collapsed,
+                Visibility = Visibility.Visible,
+                Opacity = 0,
                 IsHitTestVisible = false,
                 Child = new TextBlock
                 {
@@ -12534,7 +12534,6 @@ public partial class ChatWindow : Window
                     HorizontalAlignment = HorizontalAlignment.Left,
                     VerticalAlignment = VerticalAlignment.Top,
                     Margin = new Thickness(2, 2, 0, 0),
-                    ToolTip = "커스텀 프리셋",
                 };
                 badge.Child = new TextBlock
                 {
@@ -12634,7 +12633,8 @@ public partial class ChatWindow : Window
                 Margin = new Thickness(8, 0, 8, 6),
                 VerticalAlignment = VerticalAlignment.Bottom,
                 HorizontalAlignment = HorizontalAlignment.Stretch,
-                Visibility = Visibility.Collapsed,
+                Visibility = Visibility.Visible,
+                Opacity = 0,
                 IsHitTestVisible = false,
                 Child = new TextBlock
                 {
@@ -12712,7 +12712,8 @@ public partial class ChatWindow : Window
                 Margin = new Thickness(8, 0, 8, 6),
                 VerticalAlignment = VerticalAlignment.Bottom,
                 HorizontalAlignment = HorizontalAlignment.Stretch,
-                Visibility = Visibility.Collapsed,
+                Visibility = Visibility.Visible,
+                Opacity = 0,
                 IsHitTestVisible = false,
                 Child = new TextBlock
                 {