junction/src/Junction.App/Views/MachineConfigView.axaml

<UserControl xmlns="https://github.com/avaloniaui"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
             xmlns:vm="clr-namespace:Junction.App.ViewModels"
             mc:Ignorable="d"
             x:Class="Junction.App.Views.MachineConfigView"
             x:DataType="vm:MachineConfigViewModel"
             x:CompileBindings="True">

  <!-- header / body / footer -->
  <Grid Margin="20" RowDefinitions="Auto,*,Auto">

    <!-- Header -->
    <TextBlock Grid.Row="0" Classes="h1"
               Text="{Binding Title}"
               Margin="0,0,0,16" />

    <!-- Body: fixed form column + stretching data-items column -->
    <Grid Grid.Row="1" ColumnDefinitions="Auto,*">

      <!-- Form -->
      <Border Grid.Column="0" Classes="card" Width="380" VerticalAlignment="Top">
        <StackPanel Spacing="12">

          <StackPanel Spacing="4">
            <TextBlock Classes="fieldLabel" Text="Name" />
            <TextBox Text="{Binding Name}" Watermark="Machine name" />
          </StackPanel>

          <StackPanel Spacing="4">
            <TextBlock Classes="fieldLabel" Text="Protocol" />
            <ComboBox ItemsSource="{Binding AvailableProtocols}"
                      SelectedItem="{Binding SelectedProtocol}"
                      HorizontalAlignment="Stretch"
                      PlaceholderText="Select a protocol" />
          </StackPanel>

          <StackPanel Spacing="4">
            <TextBlock Classes="fieldLabel" Text="Agent URL" />
            <TextBox Text="{Binding AgentUrl}" Watermark="http://host:5000" />
          </StackPanel>

          <StackPanel Spacing="4">
            <TextBlock Classes="fieldLabel" Text="Poll Interval (seconds)" />
            <TextBox Text="{Binding PollIntervalSeconds}" Width="120" HorizontalAlignment="Left" />
          </StackPanel>

        </StackPanel>
      </Border>

      <!-- Data items to monitor (fills remaining width + height) -->
      <Border Grid.Column="1" Classes="card" Margin="16,0,0,0" HorizontalAlignment="Stretch">
        <DockPanel>

          <TextBlock DockPanel.Dock="Top" Classes="h2" Text="Data items to monitor"
                     Margin="0,0,0,8" />

          <!-- Controls row -->
          <StackPanel DockPanel.Dock="Top" Orientation="Horizontal" Spacing="8" Margin="0,0,0,8">
            <Button Content="Load available items"
                    Command="{Binding LoadItemsCommand}" />
            <Button Content="Select all"
                    Command="{Binding SelectAllCommand}" />
            <Button Content="Select none"
                    Command="{Binding SelectNoneCommand}" />
            <ProgressBar IsIndeterminate="True"
                         IsVisible="{Binding IsProbing}"
                         Width="120" VerticalAlignment="Center" />
          </StackPanel>

          <!-- Status message -->
          <TextBlock DockPanel.Dock="Top" Classes="subtle"
                     Text="{Binding ItemsStatus}"
                     IsVisible="{Binding HasItemsStatus}"
                     TextWrapping="Wrap" Margin="0,0,0,8" />

          <!-- Column header -->
          <Border DockPanel.Dock="Top"
                  BorderThickness="0,0,0,1"
                  BorderBrush="{DynamicResource CardBorderBrush}"
                  Padding="0,0,0,4" Margin="0,0,0,4">
            <Grid ColumnDefinitions="Auto,2*,1.2*,1.2*,1*" Margin="0,0,8,0">
              <TextBlock Grid.Column="0" Text="" Width="28" />
              <TextBlock Grid.Column="1" Classes="fieldLabel" Text="Name" />
              <TextBlock Grid.Column="2" Classes="fieldLabel" Text="Type" />
              <TextBlock Grid.Column="3" Classes="fieldLabel" Text="Category" />
              <TextBlock Grid.Column="4" Classes="fieldLabel" Text="Units" />
            </Grid>
          </Border>

          <!-- Scrollable checklist (fills remaining height) -->
          <ScrollViewer>
            <ItemsControl ItemsSource="{Binding AvailableItems}">
              <ItemsControl.ItemTemplate>
                <DataTemplate x:DataType="vm:SelectableDataItemViewModel">
                  <Grid ColumnDefinitions="Auto,2*,1.2*,1.2*,1*" Margin="0,3">
                    <CheckBox Grid.Column="0" Width="28"
                              IsChecked="{Binding IsSelected}"
                              VerticalAlignment="Center" />
                    <StackPanel Grid.Column="1" VerticalAlignment="Center">
                      <TextBlock Text="{Binding Name}" FontWeight="SemiBold" TextWrapping="Wrap" />
                      <TextBlock Text="{Binding Id}" Classes="subtle" FontSize="11" TextWrapping="Wrap" />
                    </StackPanel>
                    <TextBlock Grid.Column="2" Text="{Binding Type}" VerticalAlignment="Center" TextWrapping="Wrap" />
                    <TextBlock Grid.Column="3" Text="{Binding Category}" VerticalAlignment="Center" TextWrapping="Wrap" />
                    <TextBlock Grid.Column="4" Text="{Binding Units}" VerticalAlignment="Center" TextWrapping="Wrap" />
                  </Grid>
                </DataTemplate>
              </ItemsControl.ItemTemplate>
            </ItemsControl>
          </ScrollViewer>

        </DockPanel>
      </Border>
    </Grid>

    <!-- Footer: validation hint + action bar, full width -->
    <StackPanel Grid.Row="2" Spacing="0">
      <!-- Inline validation hint -->
      <TextBlock Text="{Binding ValidationError}"
                 IsVisible="{Binding HasValidationError}"
                 Foreground="{DynamicResource DangerBrush}"
                 TextWrapping="Wrap"
                 Margin="0,12,0,0" />

      <!-- Action bar -->
      <StackPanel Orientation="Horizontal" Spacing="12" Margin="0,16,0,0">
        <Button Classes="accent" Content="Save" Command="{Binding SaveCommand}" IsDefault="True" />
        <Button Content="Cancel" Command="{Binding CancelCommand}" />
      </StackPanel>
    </StackPanel>

  </Grid>
</UserControl>