Change Working Dir from TextBox to TextBlock in approval dialog

Simplifies the UI by using a read-only TextBlock instead of a TextBox
for the working directory field, matching other display-only fields.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: gfraiteur

src/PostSharp.Engineering.McpApprovalServer/Views/ApprovalWindow.xaml

@@ -77,12 +77,10 @@
                      MinHeight="24" />
 
             <TextBlock Grid.Row="1" Grid.Column="0" Text="Working Dir:" FontWeight="Bold" Margin="0,5" />
-            <TextBox Grid.Row="1" Grid.Column="1"
-                     Text="{Binding WorkingDirectory, Mode=OneWay}"
-                     IsReadOnly="True"
-                     FontFamily="Consolas"
-                     Background="#F5F5F5"
-                     Margin="0,5" />
+            <TextBlock Grid.Row="1" Grid.Column="1"
+                       Text="{Binding WorkingDirectory}"
+                       FontFamily="Consolas"
+                       Margin="0,5" />
 
             <TextBlock Grid.Row="2" Grid.Column="0" Text="Git Branch:" FontWeight="Bold" Margin="0,5" />
             <TextBlock Grid.Row="2" Grid.Column="1"