refactor(P5b-7): 잔여 이벤트 핸들러 전부 커맨드/behavior로 — XAML 이벤트 핸들러 0개

Microsoft.Xaml.Behaviors.Wpf 도입. MainWindow.xaml에 직접 이벤트 핸들러(Click/SelectionChanged/Drop/
MouseUp 등) 0개 — 전부 선언적 바인딩·커맨드·InvokeCommandAction으로 전환.

- 드래그앤드롭(DragOver/DragLeave/Drop) → i:EventTrigger + InvokeCommandAction(PassEventArgsToCommand),
  HandleDragOver/HandleFilesDropped(DragEventArgs) 추출.
- 동적 포맷 콤보 SelectionChanged → OutputFormatChangedCommand(OnOutputFormatSelected).
- 큐·이력 행 PreviewMouseLeftButtonUp → QueueRow/PastRowCommand(MouseButtonEventArgs, IsInsideButton 가드
  보존 + e.OriginalSource.DataContext로 항목 해소).
- ProcessQueueButton Click → ProcessQueueCommand.
- 검증: 빌드 0/0, 83 테스트 그린, publish 후 메인 창 크래시 없이 로드(behaviors self-contained 정상).
  드래그앤드롭·행 미리보기·포맷 변경 실동작은 GUI 스모크 권장(비치명적 실패 모드).

src/Directory.Packages.props

@@ -32,6 +32,7 @@
     <!-- App -->
     <PackageVersion Include="WPF-UI" Version="4.3.0" />
     <PackageVersion Include="CommunityToolkit.Mvvm" Version="8.2.2" />
+    <PackageVersion Include="Microsoft.Xaml.Behaviors.Wpf" Version="1.1.135" />
 
     <!-- Tests -->
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.11.1" />

src/Everything2Everything.App/Everything2Everything.App.csproj

@@ -22,6 +22,7 @@
   <ItemGroup>
     <PackageReference Include="WPF-UI" />
     <PackageReference Include="CommunityToolkit.Mvvm" />
+    <PackageReference Include="Microsoft.Xaml.Behaviors.Wpf" />
   </ItemGroup>
 
   <ItemGroup>

src/Everything2Everything.App/Views/MainWindow.xaml

@@ -2,6 +2,7 @@
                  xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
                  xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
                  xmlns:ui="http://schemas.lepo.co/wpfui/2022/xaml"
+                 xmlns:i="http://schemas.microsoft.com/xaml/behaviors"
                  Title="FormatShift Utility"
                  Icon="pack://application:,,,/Assets/app-icon.png"
                  Width="1280" Height="960"
@@ -11,9 +12,6 @@
                  WindowCornerPreference="Round"
                  WindowStartupLocation="CenterScreen"
                  AllowDrop="True"
-                 Drop="OnFilesDropped"
-                 DragOver="OnDragOver"
-                 DragLeave="OnDragLeave"
                  TextOptions.TextFormattingMode="Display"
                  UseLayoutRounding="True">
     <Window.Resources>
@@ -31,6 +29,18 @@
         <KeyBinding Key="F5" Command="{Binding RefreshCommand, RelativeSource={RelativeSource AncestorType=Window}}"/>
     </Window.InputBindings>
 
+    <i:Interaction.Triggers>
+        <i:EventTrigger EventName="DragOver">
+            <i:InvokeCommandAction Command="{Binding DragOverCommand, RelativeSource={RelativeSource AncestorType=Window}}" PassEventArgsToCommand="True"/>
+        </i:EventTrigger>
+        <i:EventTrigger EventName="DragLeave">
+            <i:InvokeCommandAction Command="{Binding DragLeaveCommand, RelativeSource={RelativeSource AncestorType=Window}}"/>
+        </i:EventTrigger>
+        <i:EventTrigger EventName="Drop">
+            <i:InvokeCommandAction Command="{Binding DropCommand, RelativeSource={RelativeSource AncestorType=Window}}" PassEventArgsToCommand="True"/>
+        </i:EventTrigger>
+    </i:Interaction.Triggers>
+
     <Grid Background="{StaticResource FsBgBase}">
         <Grid.RowDefinitions>
             <RowDefinition Height="32"/>
@@ -97,8 +107,13 @@
                                                    HorizontalAlignment="Center" VerticalAlignment="Center"/>
                                     </Border>
                                     <ComboBox x:Name="OutputFormatCombo" Grid.Column="1"
-                                              Margin="8,0,0,0" VerticalAlignment="Center"
+                                              Margin="8,0,0,0" VerticalAlignment="Center">
-                                              SelectionChanged="OnOutputFormatChanged"/>
+                                        <i:Interaction.Triggers>
+                                            <i:EventTrigger EventName="SelectionChanged">
+                                                <i:InvokeCommandAction Command="{Binding OutputFormatChangedCommand, RelativeSource={RelativeSource AncestorType=Window}}"/>
+                                            </i:EventTrigger>
+                                        </i:Interaction.Triggers>
+                                    </ComboBox>
                                 </Grid>
                                 <TextBlock x:Name="OutputFormatHint" Margin="0,6,0,0"
                                            Style="{StaticResource FsCaptionStyle}"
@@ -315,7 +330,7 @@
                                     Content="Idle — drop files to begin"
                                     Style="{StaticResource FsPrimaryButtonStyle}"
                                     IsEnabled="False"
-                                    Click="OnProcessQueueClick"/>
+                                    Command="{Binding ProcessQueueCommand, RelativeSource={RelativeSource AncestorType=Window}}"/>
                         </StackPanel>
                     </Border>
                 </Grid>
@@ -456,9 +471,12 @@
                                                 Background="{StaticResource FsBgPanel}"
                                                 BorderBrush="{StaticResource FsBorderSubtle}"
                                                 BorderThickness="1"
-                                                Cursor="Hand"
+                                                Cursor="Hand">
-                                                PreviewMouseLeftButtonUp="OnQueueRowClick"
+                                            <i:Interaction.Triggers>
-                                                Tag="{Binding}">
+                                                <i:EventTrigger EventName="PreviewMouseLeftButtonUp">
+                                                    <i:InvokeCommandAction Command="{Binding QueueRowCommand, RelativeSource={RelativeSource AncestorType=Window}}" PassEventArgsToCommand="True"/>
+                                                </i:EventTrigger>
+                                            </i:Interaction.Triggers>
                                             <Grid>
                                                 <Grid.ColumnDefinitions>
                                                     <ColumnDefinition Width="2"/>
@@ -570,9 +588,12 @@
                                                     <Border BorderBrush="#0DFFFFFF"
                                                             BorderThickness="0,0,0,1" Padding="0,12"
                                                             Cursor="Hand"
-                                                            Background="Transparent"
+                                                            Background="Transparent">
-                                                            PreviewMouseLeftButtonUp="OnPastRowClick"
+                                                        <i:Interaction.Triggers>
-                                                            Tag="{Binding}">
+                                                            <i:EventTrigger EventName="PreviewMouseLeftButtonUp">
+                                                                <i:InvokeCommandAction Command="{Binding PastRowCommand, RelativeSource={RelativeSource AncestorType=Window}}" PassEventArgsToCommand="True"/>
+                                                            </i:EventTrigger>
+                                                        </i:Interaction.Triggers>
                                                         <Grid>
                                                             <Grid.ColumnDefinitions>
                                                                 <ColumnDefinition Width="40"/>

src/Everything2Everything.App/Views/MainWindow.xaml.cs

@@ -53,6 +53,12 @@ public partial class MainWindow : Wpf.Ui.Controls.FluentWindow
     public ICommand TabCommand { get; }
     public ICommand ConflictRuleCommand { get; }
     public ICommand CombineToggleCommand { get; }
+    public ICommand OutputFormatChangedCommand { get; }
+    public ICommand DragOverCommand { get; }
+    public ICommand DragLeaveCommand { get; }
+    public ICommand DropCommand { get; }
+    public ICommand QueueRowCommand { get; }
+    public ICommand PastRowCommand { get; }
 
     public MainWindow(ConversionEngine engine, ISettingsStore settings, IReadOnlyList<string>? initialFiles = null)
     {
@@ -78,6 +84,12 @@ public partial class MainWindow : Wpf.Ui.Controls.FluentWindow
         TabCommand = new RelayCommand(p => ShowTab(p as string ?? "Past"));
         ConflictRuleCommand = new RelayCommand(p => SetConflictRule(p as string));
         CombineToggleCommand = new RelayCommand(_ => UpdateCombineState(SelectedOutputExtension));
+        OutputFormatChangedCommand = new RelayCommand(_ => OnOutputFormatSelected());
+        DragOverCommand = new RelayCommand(p => HandleDragOver(p as DragEventArgs));
+        DragLeaveCommand = new RelayCommand(_ => DropHintOverlay.Visibility = Visibility.Collapsed);
+        DropCommand = new RelayCommand(p => HandleFilesDropped(p as DragEventArgs));
+        QueueRowCommand = new RelayCommand(p => HandleQueueRowClick(p as MouseButtonEventArgs));
+        PastRowCommand = new RelayCommand(p => HandlePastRowClick(p as MouseButtonEventArgs));
 
         InitializeComponent();
 
@@ -164,8 +176,9 @@ public partial class MainWindow : Wpf.Ui.Controls.FluentWindow
 
     // ============== Drag & Drop ==============
 
-    private void OnDragOver(object sender, DragEventArgs e)
+    private void HandleDragOver(DragEventArgs? e)
     {
+        if (e is null) return;
         e.Effects = e.Data.GetDataPresent(DataFormats.FileDrop)
             ? DragDropEffects.Copy : DragDropEffects.None;
         DropHintOverlay.Visibility = e.Effects == DragDropEffects.Copy
@@ -173,15 +186,10 @@ public partial class MainWindow : Wpf.Ui.Controls.FluentWindow
         e.Handled = true;
     }
 
-    private void OnDragLeave(object sender, DragEventArgs e)
+    private void HandleFilesDropped(DragEventArgs? e)
     {
         DropHintOverlay.Visibility = Visibility.Collapsed;
-    }
+        if (e is null || !e.Data.GetDataPresent(DataFormats.FileDrop)) return;
-
-    private void OnFilesDropped(object sender, DragEventArgs e)
-    {
-        DropHintOverlay.Visibility = Visibility.Collapsed;
-        if (!e.Data.GetDataPresent(DataFormats.FileDrop)) return;
         if (e.Data.GetData(DataFormats.FileDrop) is not string[] paths) return;
 
         AddToQueue(ExpandPaths(paths));
@@ -308,20 +316,22 @@ public partial class MainWindow : Wpf.Ui.Controls.FluentWindow
     private string? _selectedPreviewPath;
     private CancellationTokenSource? _previewCts;
 
-    private async void OnQueueRowClick(object sender, MouseButtonEventArgs e)
+    private async void HandleQueueRowClick(MouseButtonEventArgs? e)
     {
+        if (e is null) return;
         if (e.OriginalSource is DependencyObject src && IsInsideButton(src)) return;
-        if (sender is not FrameworkElement fe || fe.Tag is not QueueItem item) return;
+        if ((e.OriginalSource as FrameworkElement)?.DataContext is not QueueItem item) return;
 
         _selectedPreviewItem = item;
         await LoadPreviewAsync(item);
         e.Handled = true;
     }
 
-    private async void OnPastRowClick(object sender, MouseButtonEventArgs e)
+    private async void HandlePastRowClick(MouseButtonEventArgs? e)
     {
+        if (e is null) return;
         if (e.OriginalSource is DependencyObject src && IsInsideButton(src)) return;
-        if (sender is not FrameworkElement fe || fe.Tag is not HistoryRow row) return;
+        if ((e.OriginalSource as FrameworkElement)?.DataContext is not HistoryRow row) return;
 
         if (row.SourcePath == "<demo>")
         {
@@ -1036,7 +1046,7 @@ public partial class MainWindow : Wpf.Ui.Controls.FluentWindow
         };
     }
 
-    private void OnOutputFormatChanged(object sender, SelectionChangedEventArgs e)
+    private void OnOutputFormatSelected()
     {
         if (_suppressFormatChanged) return;
         if (OutputFormatCombo.SelectedItem is ComboBoxItem item && item.Tag is string ext)