에이전트 루프 진단과 문서 golden 회귀를 마감한다

- AgentLoopService의 컨텍스트 압축 완료 메시지와 query-view 요약 문자열 조립을 AgentLoopDiagnosticsFormatter로 분리해 루프 본체의 책임을 더 줄였다.

- ChatStorageService 로드 경로에서 legacy .axchat의 누락된 tool_result preview를 synthetic preview로 즉시 복원하도록 보강했다.

- HTML/DOCX golden 회귀와 legacy 저장 경로 회귀 테스트를 추가해 PPTX/XLSX에 이어 문서 품질 고정 범위를 확대했다.

- 검증: dotnet build src/AxCopilot/AxCopilot.csproj -c Release -v minimal -p:OutputPath=bin\verify_loop_storage_golden\ -p:IntermediateOutputPath=obj\verify_loop_storage_golden\ (경고 0, 오류 0)

- 검증: dotnet test src/AxCopilot.Tests/AxCopilot.Tests.csproj -c Release -v minimal --filter AgentLoopDiagnosticsFormatterTests|ChatStorageServiceTests|HtmlSkillGoldenReportTests|DocxSkillGoldenDocumentTests|AgentMessageInvariantHelperTests|PptxSkillGoldenDeckTests|ExcelSkillGoldenWorkbookTests -p:OutputPath=bin\verify_loop_storage_golden_tests\ -p:IntermediateOutputPath=obj\verify_loop_storage_golden_tests\ (통과 10)

src/AxCopilot/Services/Agent/AgentLoopService.cs

@@ -475,13 +475,10 @@ public partial class AgentLoopService
                     if (compactionResult.Changed)
                     {
                         MarkRunPostCompaction(compactionResult, runState);
-                        var compactSummary = !string.IsNullOrWhiteSpace(compactionResult.StageSummary)
-                            ? compactionResult.StageSummary
-                            : "기본";
                         EmitEvent(
                             AgentEventType.Thinking,
                             "",
-                            $"컨텍스트 압축 완료 — {compactSummary} · {Services.TokenEstimator.Format(compactionResult.SavedTokens)} tokens 절감");
+                            AgentLoopDiagnosticsFormatter.BuildCompactionCompleteMessage(compactionResult));
                     }
                 }
 
@@ -505,19 +502,12 @@ public partial class AgentLoopService
                 var queryMessages = queryView.Messages;
                 if (queryView.BoundaryApplied || queryView.ToolPairExpanded || queryView.TruncatedToolResultCount > 0)
                 {
-                    var queryViewSummary =
-                        $"query-view {queryView.SourceMessageCount}->{queryView.ViewMessageCount}, " +
-                        $"start={queryView.WindowStartIndex}, " +
-                        $"pairs={queryView.PreservedToolPairCount}, " +
-                        $"tool_result_budget={queryView.TruncatedToolResultCount}, " +
-                        $"tool_result_preview_reuse={queryView.ReusedToolResultPreviewCount}, " +
-                        $"tokens {queryView.TokensBeforeBudget}->{queryView.TokensAfterBudget}";
                     WorkflowLogService.LogTransition(
                         _conversationId,
                         _currentRunId,
                         iteration,
                         "query_view",
-                        queryViewSummary);
+                        AgentLoopDiagnosticsFormatter.BuildQueryViewSummary(queryView));
                 }
 
                 var isDebugLog = string.Equals(_settings.Settings.Llm.AgentLogLevel, "debug", StringComparison.OrdinalIgnoreCase);