AX Agent footer 작업 바 chip 스타일 통일 및 후속 polish

- ChatWindow에 FooterChipBtn 스타일을 추가해 하단 작업 바 버튼 언어를 공통화
- 권한과 Git 브랜치 버튼이 같은 라운드/테두리/패딩 규칙을 사용하도록 정리
- README와 DEVELOPMENT 문서에 2026-04-06 11:34 (KST) 기준 footer polish 반영
- dotnet build 검증 경고 0, 오류 0 확인

src/AxCopilot/Views/ChatWindow.xaml

@@ -245,6 +245,32 @@
                 </Setter.Value>
             </Setter>
         </Style>
+        <Style x:Key="FooterChipBtn" TargetType="Button" BasedOn="{StaticResource OutlineHoverBtn}">
+            <Setter Property="Padding" Value="10,5"/>
+            <Setter Property="MinHeight" Value="30"/>
+            <Setter Property="Template">
+                <Setter.Value>
+                    <ControlTemplate TargetType="Button">
+                        <Border x:Name="Bd"
+                                Background="{DynamicResource LauncherBackground}"
+                                BorderBrush="{DynamicResource BorderColor}"
+                                BorderThickness="1"
+                                CornerRadius="10"
+                                Padding="{TemplateBinding Padding}">
+                            <ContentPresenter HorizontalAlignment="Center" VerticalAlignment="Center"/>
+                        </Border>
+                        <ControlTemplate.Triggers>
+                            <Trigger Property="IsMouseOver" Value="True">
+                                <Setter TargetName="Bd" Property="Background" Value="{DynamicResource ItemHoverBackground}"/>
+                            </Trigger>
+                            <Trigger Property="IsEnabled" Value="False">
+                                <Setter Property="Opacity" Value="0.35"/>
+                            </Trigger>
+                        </ControlTemplate.Triggers>
+                    </ControlTemplate>
+                </Setter.Value>
+            </Setter>
+        </Style>
         <Style x:Key="SettingsNavBtn" TargetType="RadioButton">
             <Setter Property="Foreground" Value="{DynamicResource SecondaryText}"/>
             <Setter Property="FontSize" Value="11.5"/>
@@ -2185,7 +2211,7 @@
                                 <!-- 폴더 데이터 활용은 코드/코워크 자동 정책으로만 동작 -->
 
                                 <!-- 권한 메뉴 -->
-                                <Button x:Name="BtnPermission" Grid.Column="7" Style="{StaticResource OutlineHoverBtn}"
+                                <Button x:Name="BtnPermission" Grid.Column="7" Style="{StaticResource FooterChipBtn}"
                                         Padding="10,5" Click="BtnPermission_Click" ToolTip="파일 접근 권한">
                                     <StackPanel Orientation="Horizontal">
                                         <TextBlock x:Name="PermissionIcon" Text="&#xE8D7;" FontFamily="Segoe MDL2 Assets" FontSize="12"
@@ -2203,7 +2229,7 @@
 
                                 <Button x:Name="BtnGitBranch"
                                         Grid.Column="9"
-                                        Style="{StaticResource GhostBtn}"
+                                        Style="{StaticResource FooterChipBtn}"
                                         Padding="10,5"
                                         Margin="2,0,0,0"
                                         Visibility="Collapsed"