Hide modal dialogs from the taskbar

Avalonia windows default to ShowInTaskbar=true, so every owned modal
dialog (Open from GAC/NuGet feed/running process, Manage Assembly
Lists, Export Project, Create List, Set Target Framework) got its own
taskbar button, which is not standard Windows behavior. The assertion
and crash dialogs intentionally keep their buttons so an interrupted
session stays easy to find.

Assisted-by: Claude:claude-fable-5:Claude Code

ILSpy/Views/CreateListDialog.axaml

@@ -3,6 +3,7 @@
         x:Class="ICSharpCode.ILSpy.Views.CreateListDialog"
         Width="320" Height="160" CanResize="False"
         WindowStartupLocation="CenterOwner"
+        ShowInTaskbar="False"
         Title="ILSpy">
 	<Grid Margin="12,8" RowDefinitions="Auto,Auto,*,Auto">
 		<TextBlock Grid.Row="0" Text="Enter the name of the list:" Margin="0,0,0,6" />

ILSpy/Views/ExportProjectDialog.axaml

@@ -5,6 +5,7 @@
         Width="560" MinWidth="460" MinHeight="440" MaxHeight="900"
         SizeToContent="Height"
         WindowStartupLocation="CenterOwner"
+        ShowInTaskbar="False"
         Title="Export Project">
 	<DockPanel Margin="12">
 		<StackPanel DockPanel.Dock="Bottom" Orientation="Horizontal" HorizontalAlignment="Right"

ILSpy/Views/ManageAssemblyListsDialog.axaml

@@ -3,6 +3,7 @@
         x:Class="ICSharpCode.ILSpy.Views.ManageAssemblyListsDialog"
         Width="480" Height="350" MinWidth="480" MinHeight="250"
         WindowStartupLocation="CenterOwner"
+        ShowInTaskbar="False"
         Title="Manage Assembly Lists">
 	<Grid Margin="12,8" ColumnDefinitions="*,Auto" RowDefinitions="*,Auto">
 		<ListBox Grid.Row="0" Grid.Column="0" Name="ListsBox" Margin="0,8,8,8" SelectionMode="Single" />

ILSpy/Views/OpenFromGacDialog.axaml

@@ -3,6 +3,7 @@
         x:Class="ICSharpCode.ILSpy.Views.OpenFromGacDialog"
         Width="750" Height="350" MinWidth="200" MinHeight="150"
         WindowStartupLocation="CenterOwner"
+        ShowInTaskbar="False"
         CanResize="True">
 	<Grid Margin="12,8" RowDefinitions="Auto,*,Auto" RowSpacing="6">
 		<Grid Grid.Row="0" ColumnDefinitions="Auto,*">

ILSpy/Views/OpenFromNuGetFeedDialog.axaml

@@ -6,6 +6,7 @@
         x:DataType="vm:OpenFromNuGetFeedDialogViewModel"
         Width="1000" Height="650" MinWidth="700" MinHeight="400"
         WindowStartupLocation="CenterOwner"
+        ShowInTaskbar="False"
         CanResize="True">
 	<Grid Margin="12,8" RowDefinitions="Auto,*,Auto,Auto" RowSpacing="8">
 

ILSpy/Views/OpenFromProcessDialog.axaml

@@ -5,6 +5,7 @@
         x:DataType="vm:OpenFromProcessDialogViewModel"
         Width="850" Height="560" MinWidth="500" MinHeight="360"
         WindowStartupLocation="CenterOwner"
+        ShowInTaskbar="False"
         CanResize="True">
 	<!-- Both lists are ListBoxes rather than DataGrids. A DataGrid derives its scroll extent
 	     from the current scroll offset, so an offset that is briefly too large inflates the

ILSpy/Views/SetTargetFrameworkDialog.axaml

@@ -3,6 +3,7 @@
         x:Class="ICSharpCode.ILSpy.Views.SetTargetFrameworkDialog"
         Width="360" SizeToContent="Height" CanResize="False"
         WindowStartupLocation="CenterOwner"
+        ShowInTaskbar="False"
         Title="ILSpy">
 	<Grid Margin="12,10" RowDefinitions="Auto,Auto,Auto,Auto,Auto">
 		<TextBlock Grid.Row="0" Name="PromptText" Margin="0,0,0,6" TextWrapping="Wrap" />