feat: 메인 창 사이드바에 변환 진행 표시 패널 추가

ProcessQueueButton 위에 ProcessingProgressPanel:
- 현재 변환 중인 파일명 (이름만, ellipsis 처리)
- N / Total 카운터
- 0~100% ProgressBar (Index + FileProgress 기준 누적)
- % 텍스트

ShowProcessingProgress(total) → 변환 시작 시 표시,
UpdateProcessingProgress(p) → reporter 콜백에서 실시간 갱신,
HideProcessingProgress() → finally에서 숨김

src/Everything2Everything.App/Views/MainWindow.xaml

@@ -233,6 +233,36 @@
                             <TextBlock x:Name="CapabilityStatusText" Margin="0,0,0,12"
                                        Style="{StaticResource FsCaptionStyle}"
                                        TextWrapping="Wrap" Visibility="Collapsed"/>
+
+                            <!-- Conversion progress (shown only while processing) -->
+                            <StackPanel x:Name="ProcessingProgressPanel" Margin="0,0,0,12"
+                                        Visibility="Collapsed">
+                                <Grid Margin="0,0,0,6">
+                                    <Grid.ColumnDefinitions>
+                                        <ColumnDefinition Width="*"/>
+                                        <ColumnDefinition Width="Auto"/>
+                                    </Grid.ColumnDefinitions>
+                                    <TextBlock x:Name="ProcessingFileLabel"
+                                               Style="{StaticResource FsCaptionStyle}"
+                                               Foreground="{StaticResource FsTextPrimary}"
+                                               TextTrimming="CharacterEllipsis"
+                                               Text="처리 중…"/>
+                                    <TextBlock x:Name="ProcessingCountLabel" Grid.Column="1"
+                                               Margin="8,0,0,0"
+                                               FontFamily="{StaticResource FsFontMono}" FontSize="11"
+                                               Foreground="{StaticResource FsAccentBlue}"
+                                               Text="0 / 0"/>
+                                </Grid>
+                                <ProgressBar x:Name="ProcessingProgressBar"
+                                             Height="6" Minimum="0" Maximum="100" Value="0"/>
+                                <TextBlock x:Name="ProcessingPercentLabel"
+                                           Margin="0,4,0,0"
+                                           FontFamily="{StaticResource FsFontMono}" FontSize="10"
+                                           Foreground="{StaticResource FsTextSecondary}"
+                                           HorizontalAlignment="Right"
+                                           Text="0%"/>
+                            </StackPanel>
+
                             <Button x:Name="ProcessQueueButton"
                                     Content="Idle — drop files to begin"
                                     Style="{StaticResource FsPrimaryButtonStyle}"

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

@@ -515,6 +515,7 @@ public partial class MainWindow : Wpf.Ui.Controls.FluentWindow
 
         _cts = new CancellationTokenSource();
         UpdateProcessQueueButton();
+        ShowProcessingProgress(snapshot.Count);
 
         var engine = ((App)Application.Current).Engine;
         var options = BuildOptions();
@@ -527,6 +528,7 @@ public partial class MainWindow : Wpf.Ui.Controls.FluentWindow
                 else if (i == p.Index) snapshot[i].SetState($"{(int)(p.FileProgress * 100)}%");
                 else snapshot[i].SetState("queued");
             }
+            UpdateProcessingProgress(p);
         });
 
         try
@@ -573,10 +575,41 @@ public partial class MainWindow : Wpf.Ui.Controls.FluentWindow
             UpdateProcessQueueButton();
             UpdateActiveQueueVisibility();
             ApplyAppDataStats();
+            HideProcessingProgress();
             if (_activeQueue.Count == 0) ShowTab("Past");
         }
     }
 
+    private void ShowProcessingProgress(int totalCount)
+    {
+        if (ProcessingProgressPanel is null) return;
+        ProcessingProgressPanel.Visibility = Visibility.Visible;
+        ProcessingProgressBar.Value = 0;
+        ProcessingPercentLabel.Text = "0%";
+        ProcessingCountLabel.Text = $"0 / {totalCount}";
+        ProcessingFileLabel.Text = "준비 중…";
+    }
+
+    private void UpdateProcessingProgress(ConvertProgress p)
+    {
+        if (ProcessingProgressPanel is null) return;
+        var total = Math.Max(1, p.Total);
+        var overall = ((p.Index + p.FileProgress) / total) * 100.0;
+        overall = Math.Clamp(overall, 0, 100);
+        ProcessingProgressBar.Value = overall;
+        ProcessingPercentLabel.Text = $"{overall:0.#}%";
+        ProcessingCountLabel.Text = $"{Math.Min(p.Index + 1, p.Total)} / {p.Total}";
+        ProcessingFileLabel.Text = string.IsNullOrEmpty(p.CurrentPath)
+            ? "처리 중…"
+            : Path.GetFileName(p.CurrentPath);
+    }
+
+    private void HideProcessingProgress()
+    {
+        if (ProcessingProgressPanel is null) return;
+        ProcessingProgressPanel.Visibility = Visibility.Collapsed;
+    }
+
     // ============== History ==============
 
     private void AddToHistory(HistoryEntry entry)