구조 개선: transcript 지연 가상화와 tool executor 분리 적용

이번 변경은 claude-code 기준 구조 강건성을 높이기 위한 리팩터링입니다.

핵심 수정 사항:

- AX Agent transcript를 TranscriptVisualItem/TranscriptVisualHost 기반 지연 materialization 구조로 전환해 MessageList 가상화 기반을 강화했습니다.

- StreamingToolExecutionCoordinator를 IToolExecutionCoordinator 뒤로 분리해 AgentLoopService가 구체 구현에 직접 묶이지 않도록 정리했습니다.

- 라이브 진행 카드 렌더를 ChatWindow.LiveProgressPresentation partial로 이동해 ChatWindow.xaml.cs의 책임을 더 줄였습니다.

- 기존 메시지 bubble 조립 로직을 유지하면서 transcript host가 필요 시점에 bubble을 만들 수 있도록 helper 경로를 추가했습니다.

검증 결과:

- dotnet build src/AxCopilot/AxCopilot.csproj -c Release -v minimal -p:OutputPath=bin\\verify\\ -p:IntermediateOutputPath=obj\\verify\

- 경고 0 / 오류 0

src/AxCopilot/Views/ChatWindow.xaml.cs

@@ -3530,6 +3530,7 @@ public partial class ChatWindow : Window
 
     private void ShowDropActionMenu(string[] files)
     {
+        if (files == null || files.Length == 0) return;
         // 파일 유형 판별
         var ext = System.IO.Path.GetExtension(files[0]).ToLowerInvariant();
         string category;
@@ -4243,7 +4244,9 @@ public partial class ChatWindow : Window
         if (string.IsNullOrWhiteSpace(raw) || string.Equals(raw, command, StringComparison.OrdinalIgnoreCase))
             return ("open", "");
         var parts = raw.Split(' ', StringSplitOptions.RemoveEmptyEntries);
-        if (parts.Length <= 1)
+        if (parts.Length == 0)
+            return ("open", "");
+        if (parts.Length == 1)
             return (parts[0].Trim().ToLowerInvariant(), "");
         return (parts[0].Trim().ToLowerInvariant(), string.Join(' ', parts.Skip(1)).Trim());
     }
@@ -5515,7 +5518,8 @@ public partial class ChatWindow : Window
     }
 
     private AgentLoopService GetAgentLoop(string tab) =>
-        _agentLoops.TryGetValue(tab, out var loop) ? loop : _agentLoops.Values.First();
+        _agentLoops.TryGetValue(tab, out var loop) ? loop : _agentLoops.Values.FirstOrDefault()
+            ?? throw new InvalidOperationException($"No agent loop registered for tab '{tab}'");
 
     private async Task<string> RunAgentLoopAsync(
         string runTab,
@@ -6840,200 +6844,6 @@ public partial class ChatWindow : Window
 
     // ─── 채팅창 내 에이전트 라이브 진행 카드 ─────────────────────────────────────
 
-    private void ShowAgentLiveCard(string runTab)
-    {
-        if (MessageList == null) return;
-        if (!string.Equals(runTab, _activeTab, StringComparison.OrdinalIgnoreCase)) return;
-
-        RemoveAgentLiveCard(animated: false); // 기존 카드 즉시 제거
-
-        _agentLiveStartTime = DateTime.UtcNow;
-        _agentLiveSubItemTexts.Clear();
-        _agentLiveCurrentCategory = null;
-
-        var msgMaxWidth = GetMessageMaxWidth();
-        var secondaryText = TryFindResource("SecondaryText") as Brush ?? Brushes.Gray;
-        var borderBrush = TryFindResource("BorderColor") as Brush ?? Brushes.Gray;
-        var accentBrush = TryFindResource("AccentColor") as Brush ?? Brushes.CornflowerBlue;
-
-        var container = new StackPanel
-        {
-            HorizontalAlignment = HorizontalAlignment.Center,
-            Width = msgMaxWidth,
-            MaxWidth = msgMaxWidth,
-            Margin = new Thickness(0, 4, 0, 6),
-            Opacity = IsLightweightLiveProgressMode(runTab) ? 1 : 0,
-            RenderTransform = IsLightweightLiveProgressMode(runTab)
-                ? Transform.Identity
-                : new TranslateTransform(0, 8),
-        };
-        if (!IsLightweightLiveProgressMode(runTab))
-        {
-            container.BeginAnimation(UIElement.OpacityProperty,
-                new DoubleAnimation(0, 1, TimeSpan.FromMilliseconds(260)));
-            ((TranslateTransform)container.RenderTransform).BeginAnimation(
-                TranslateTransform.YProperty,
-                new DoubleAnimation(8, 0, TimeSpan.FromMilliseconds(280))
-                { EasingFunction = new System.Windows.Media.Animation.QuadraticEase
-                    { EasingMode = System.Windows.Media.Animation.EasingMode.EaseOut } });
-        }
-
-        // 헤더: 펄싱 아이콘 + 에이전트 이름 + 경과 시간
-        var headerGrid = new Grid { Margin = new Thickness(2, 0, 0, 3) };
-        headerGrid.ColumnDefinitions.Add(new ColumnDefinition { Width = GridLength.Auto });
-        headerGrid.ColumnDefinitions.Add(new ColumnDefinition { Width = GridLength.Auto });
-        headerGrid.ColumnDefinitions.Add(new ColumnDefinition { Width = new GridLength(1, GridUnitType.Star) });
-
-        var liveIcon = CreateMiniLauncherIcon(pixelSize: 4.0);
-        if (!IsLightweightLiveProgressMode(runTab))
-        {
-            liveIcon.BeginAnimation(UIElement.OpacityProperty,
-                new DoubleAnimation(1.0, 0.35, TimeSpan.FromMilliseconds(750))
-                { AutoReverse = true, RepeatBehavior = System.Windows.Media.Animation.RepeatBehavior.Forever,
-                  EasingFunction = new System.Windows.Media.Animation.SineEase() });
-        }
-        Grid.SetColumn(liveIcon, 0);
-        headerGrid.Children.Add(liveIcon);
-
-        var (agentName, _, _) = GetAgentIdentity();
-        var nameTb = new TextBlock
-        {
-            Text = agentName,
-            FontSize = 11,
-            FontWeight = FontWeights.SemiBold,
-            Foreground = secondaryText,
-            Margin = new Thickness(6, 0, 0, 0),
-            VerticalAlignment = VerticalAlignment.Center,
-        };
-        Grid.SetColumn(nameTb, 1);
-        headerGrid.Children.Add(nameTb);
-
-        _agentLiveElapsedText = new TextBlock
-        {
-            Text = "",
-            FontSize = 10,
-            Foreground = secondaryText,
-            Opacity = 0.50,
-            HorizontalAlignment = HorizontalAlignment.Right,
-            VerticalAlignment = VerticalAlignment.Center,
-        };
-        Grid.SetColumn(_agentLiveElapsedText, 2);
-        headerGrid.Children.Add(_agentLiveElapsedText);
-        container.Children.Add(headerGrid);
-
-        // 내용 카드
-        var card = new Border
-        {
-            BorderBrush = borderBrush,
-            BorderThickness = new Thickness(1),
-            CornerRadius = new CornerRadius(12),
-            Padding = new Thickness(13, 10, 13, 10),
-        };
-        card.SetResourceReference(Border.BackgroundProperty, "ItemBackground");
-
-        var cardStack = new StackPanel();
-
-        _agentLiveStatusText = new TextBlock
-        {
-            Text = "준비 중...",
-            FontSize = 12,
-            FontFamily = new System.Windows.Media.FontFamily("Segoe UI, Malgun Gothic"),
-            Foreground = secondaryText,
-            TextWrapping = TextWrapping.Wrap,
-        };
-        cardStack.Children.Add(_agentLiveStatusText);
-
-        _agentLiveSubItems = new StackPanel { Margin = new Thickness(0, 6, 0, 0) };
-        cardStack.Children.Add(_agentLiveSubItems);
-
-        card.Child = cardStack;
-        container.Children.Add(card);
-
-        _agentLiveContainer = container;
-        AddTranscriptElement(container);
-        ForceScrollToEnd();
-
-        // 경과 시간 타이머
-        _agentLiveElapsedTimer = new DispatcherTimer { Interval = TimeSpan.FromSeconds(1) };
-        _agentLiveElapsedTimer.Tick += (_, _) =>
-        {
-            if (_agentLiveElapsedText != null)
-            {
-                var sec = (int)(DateTime.UtcNow - _agentLiveStartTime).TotalSeconds;
-                _agentLiveElapsedText.Text = sec > 0 ? $"{sec}초 경과" : "";
-            }
-        };
-        _agentLiveElapsedTimer.Start();
-    }
-
-    private void UpdateAgentLiveCard(string message, string? subItem = null,
-                                     string? category = null, bool clearSubItems = false)
-    {
-        if (_agentLiveContainer == null || _agentLiveStatusText == null) return;
-
-        _agentLiveStatusText.Text = message;
-
-        if (clearSubItems || (category != null && category != _agentLiveCurrentCategory))
-        {
-            _agentLiveSubItemTexts.Clear();
-            _agentLiveSubItems?.Children.Clear();
-            if (category != null) _agentLiveCurrentCategory = category;
-        }
-
-        if (!string.IsNullOrEmpty(subItem) && !_agentLiveSubItemTexts.Contains(subItem))
-        {
-            _agentLiveSubItemTexts.Add(subItem);
-            const int maxLiveSubItems = 8;
-            if (_agentLiveSubItemTexts.Count > maxLiveSubItems)
-            {
-                _agentLiveSubItemTexts.RemoveAt(0);
-                if (_agentLiveSubItems?.Children.Count > 0)
-                    _agentLiveSubItems.Children.RemoveAt(0);
-            }
-
-            var secondary = TryFindResource("SecondaryText") as Brush ?? Brushes.Gray;
-            var tb = new TextBlock
-            {
-                Text = $"› {subItem}",
-                FontSize = 10.5,
-                FontFamily = new System.Windows.Media.FontFamily("Segoe UI, Malgun Gothic"),
-                Foreground = secondary,
-                Opacity = 0.62,
-                TextTrimming = TextTrimming.CharacterEllipsis,
-                MaxWidth = 520,
-                Margin = new Thickness(0, 1, 0, 0),
-            };
-            _agentLiveSubItems?.Children.Add(tb);
-            ForceScrollToEnd();
-        }
-    }
-
-    private void RemoveAgentLiveCard(bool animated = true)
-    {
-        _agentLiveElapsedTimer?.Stop();
-        _agentLiveElapsedTimer = null;
-
-        if (_agentLiveContainer == null) return;
-        var toRemove = _agentLiveContainer;
-        _agentLiveContainer = null;
-        _agentLiveStatusText = null;
-        _agentLiveSubItems = null;
-        _agentLiveElapsedText = null;
-        _agentLiveSubItemTexts.Clear();
-        _agentLiveCurrentCategory = null;
-
-        if (animated && ContainsTranscriptElement(toRemove) && !IsLightweightLiveProgressMode())
-        {
-            var anim = new DoubleAnimation(toRemove.Opacity, 0, TimeSpan.FromMilliseconds(160));
-            anim.Completed += (_, _) => RemoveTranscriptElement(toRemove);
-            toRemove.BeginAnimation(UIElement.OpacityProperty, anim);
-        }
-        else
-        {
-            RemoveTranscriptElement(toRemove);
-        }
-    }
-
     // ─── 미니 다이아몬드 아이콘 애니메이션 ───────────────────────────────────────
 
     private void StartStatusDiamondAnimation()