AX Agent transcript 렌더 계획/적용 구조를 분리해 유지보수성을 높이고 문서를 갱신한다

- ChatWindow transcript 렌더를 planner/execution 단계로 분리해 RenderMessages 오케스트레이션을 단순화함
- TranscriptRenderPlanner/TranscriptRenderExecution partial을 추가해 planning과 host 적용 책임을 나눔
- README와 DEVELOPMENT 문서에 2026-04-09 09:37 (KST) 기준 구조 개선 이력을 반영함
- dotnet build src/AxCopilot/AxCopilot.csproj -c Release -v minimal -p:OutputPath=bin\\verify\\ -p:IntermediateOutputPath=obj\\verify\\ 검증 결과 경고 0개 오류 0개

src/AxCopilot/Views/ChatWindow.TranscriptRendering.cs

@@ -1,6 +1,5 @@
 using System.Windows.Threading;
 using AxCopilot.Models;
-using AxCopilot.Services;
 
 namespace AxCopilot.Views;
 
@@ -58,96 +57,15 @@ public partial class ChatWindow
             InvalidateTimelineCache();
         }
 
-        var showHistory = conv.ShowExecutionHistory;
         EmptyState.Visibility = System.Windows.Visibility.Collapsed;
+        var renderPlan = BuildTranscriptRenderPlan(conv, visibleMessages, visibleEvents);
 
-        var orderedTimeline = BuildTimelineRenderActions(visibleMessages, visibleEvents);
-        var effectiveRenderLimit = GetActiveTimelineRenderLimit();
-        var hiddenCount = Math.Max(0, orderedTimeline.Count - effectiveRenderLimit);
-        var visibleTimeline = hiddenCount > 0
-            ? orderedTimeline.GetRange(hiddenCount, orderedTimeline.Count - hiddenCount)
-            : orderedTimeline;
-        var newKeys = new List<string>(visibleTimeline.Count);
-        foreach (var t in visibleTimeline)
-            newKeys.Add(t.Key);
+        if (!TryApplyIncrementalTranscriptRender(renderPlan))
+            ApplyFullTranscriptRender(renderPlan);
 
-        var incremented = false;
-        var hasExternalChildren = _agentLiveContainer != null && ContainsTranscriptElement(_agentLiveContainer);
-        var expectedChildCount = _lastRenderedTimelineKeys.Count + (_lastRenderedHiddenCount > 0 ? 1 : 0);
-        var canIncremental = !hasExternalChildren
-            && _lastRenderedTimelineKeys.Count > 0
-            && newKeys.Count >= _lastRenderedTimelineKeys.Count
-            && _lastRenderedHiddenCount == hiddenCount
-            && GetTranscriptElementCount() == expectedChildCount;
-
-        if (canIncremental)
-        {
-            var prevLiveCount = 0;
-            for (var i = _lastRenderedTimelineKeys.Count - 1; i >= 0; i--)
-            {
-                if (_lastRenderedTimelineKeys[i].StartsWith("_live_", StringComparison.Ordinal))
-                    prevLiveCount++;
-                else
-                    break;
-            }
-
-            var prevStableCount = _lastRenderedTimelineKeys.Count - prevLiveCount;
-            var prefixMatch = true;
-            for (var i = 0; i < prevStableCount; i++)
-            {
-                if (i >= newKeys.Count || !string.Equals(_lastRenderedTimelineKeys[i], newKeys[i], StringComparison.Ordinal))
-                {
-                    prefixMatch = false;
-                    break;
-                }
-            }
-
-            if (prefixMatch)
-            {
-                try
-                {
-                    for (var r = 0; r < prevLiveCount && GetTranscriptElementCount() > 0; r++)
-                        RemoveTranscriptElementAt(GetTranscriptElementCount() - 1);
-
-                    for (var i = prevStableCount; i < visibleTimeline.Count; i++)
-                        visibleTimeline[i].Render();
-
-                    _lastRenderedTimelineKeys = newKeys;
-                    _lastRenderedHiddenCount = hiddenCount;
-                    _lastRenderedMessageCount = visibleMessages.Count;
-                    _lastRenderedEventCount = visibleEvents.Count;
-                    _lastRenderedShowHistory = showHistory;
-                    incremented = true;
-                }
-                catch (Exception ex)
-                {
-                    LogService.Warn($"증분 렌더링 실패, 전체 재빌드로 전환: {ex.Message}");
-                    _lastRenderedTimelineKeys.Clear();
-                    incremented = false;
-                }
-            }
-        }
-
-        if (!incremented)
-        {
-            ClearTranscriptElements();
-            _runBannerAnchors.Clear();
-
-            if (hiddenCount > 0)
-                AddTranscriptElement(CreateTimelineLoadMoreCard(hiddenCount));
-
-            foreach (var item in visibleTimeline)
-                item.Render();
-
-            if (_agentLiveContainer != null && !ContainsTranscriptElement(_agentLiveContainer))
-                AddTranscriptElement(_agentLiveContainer);
-
-            _lastRenderedTimelineKeys = newKeys;
-            _lastRenderedHiddenCount = hiddenCount;
-            _lastRenderedMessageCount = visibleMessages.Count;
-            _lastRenderedEventCount = visibleEvents.Count;
-            _lastRenderedShowHistory = showHistory;
-        }
+        _lastRenderedMessageCount = visibleMessages.Count;
+        _lastRenderedEventCount = visibleEvents.Count;
+        _lastRenderedShowHistory = renderPlan.ShowHistory;
 
         if (!preserveViewport)
         {