AX Agent 컨텍스트 토큰 심볼 잘림 및 hover 라벨 닫힘 개선

- 하단 컨텍스트 토큰 카드 외곽 크기와 내부 원형 그리드 여백을 조정해 파이 심볼 왼쪽 잘림 인상 보정
- usage arc 및 threshold marker 계산 중심점을 실제 심볼 크기에 맞게 재설정
- hover popup을 비상호작용 툴팁 형태로 바꿔 카드 밖으로 벗어나면 더 자연스럽게 닫히도록 정리
- README 및 DEVELOPMENT 문서에 2026-04-05 23:55 (KST) 기준 변경 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 확인

src/AxCopilot/Views/ChatWindow.xaml

@@ -1744,9 +1744,9 @@
                                     <Border x:Name="TokenUsageCard"
                                             Grid.Column="2"
                                             Margin="6,0,0,0"
-                                            Padding="0"
-                                            Width="28"
-                                            Height="28"
+                                            Padding="1"
+                                            Width="30"
+                                            Height="30"
                                             CornerRadius="999"
                                             BorderBrush="{DynamicResource BorderColor}"
                                             BorderThickness="1"
@@ -1757,7 +1757,7 @@
                                             MouseEnter="TokenUsageCard_MouseEnter"
                                             MouseLeave="TokenUsageCard_MouseLeave">
                                         <Grid>
-                                                <Grid Width="28" Height="28" VerticalAlignment="Center">
+                                                <Grid Width="28" Height="28" VerticalAlignment="Center" HorizontalAlignment="Center">
                                                 <Ellipse Stroke="{DynamicResource BorderColor}"
                                                          StrokeThickness="2.5"/>
                                                 <Path x:Name="TokenUsageArc"
@@ -1829,8 +1829,7 @@
                                                 CornerRadius="12"
                                                 Padding="12,10"
                                                 MinWidth="186"
-                                                MouseEnter="TokenUsagePopup_MouseEnter"
-                                                MouseLeave="TokenUsagePopup_MouseLeave">
+                                                IsHitTestVisible="False">
                                             <Border.Effect>
                                                 <DropShadowEffect BlurRadius="10" ShadowDepth="0" Opacity="0.08"/>
                                             </Border.Effect>

src/AxCopilot/Views/ChatWindow.xaml.cs

@@ -18691,8 +18691,8 @@ private static (string icon, string label, string bgHex, string fgHex) GetDecisi
         }
         TokenUsageCard.ToolTip = null;
 
-        UpdateCircularUsageArc(TokenUsageArc, usageRatio, 18, 18, 14);
-        PositionThresholdMarker(TokenUsageThresholdMarker, triggerRatio, 18, 18, 14, 3);
+        UpdateCircularUsageArc(TokenUsageArc, usageRatio, 14, 14, 11);
+        PositionThresholdMarker(TokenUsageThresholdMarker, triggerRatio, 14, 14, 11, 2.5);
     }
 
     private void TokenUsageCard_MouseEnter(object sender, MouseEventArgs e)
@@ -18711,8 +18711,6 @@ private static (string icon, string label, string bgHex, string fgHex) GetDecisi
     private void TokenUsagePopup_MouseEnter(object sender, MouseEventArgs e)
     {
         _tokenUsagePopupCloseTimer.Stop();
-        if (TokenUsagePopup != null)
-            TokenUsagePopup.IsOpen = true;
     }
 
     private void TokenUsagePopup_MouseLeave(object sender, MouseEventArgs e)