fix: add groupName to ExecutionDetail, rewrite ExchangeDetail to match mock

- Add groupName field to ExecutionDetail record and DetailService
- Dashboard: fix TDZ error (rows referenced before definition), add
  selectedRow fallback for diagram groupName lookup
- ExchangeDetail: rewrite to match mock layout — auto-select first
  processor, Message IN/OUT split panels with header key-value rows,
  error panel for failed processors, Timeline/Flow toggle buttons
- Track diagram-mapping utility (was untracked, caused CI build failure)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/pages/Dashboard/Dashboard.tsx

@@ -40,13 +40,15 @@ export default function Dashboard() {
     offset: 0, limit: 50,
   }, true);
   const { data: detail } = useExecutionDetail(selectedId);
-  const { data: diagram } = useDiagramByRoute(detail?.groupName, detail?.routeId);
 
   const rows: Row[] = useMemo(() =>
     (searchResult?.data || []).map((e: ExecutionSummary) => ({ ...e, id: e.executionId })),
     [searchResult],
   );
 
+  const selectedRow = rows.find(r => r.id === selectedId);
+  const { data: diagram } = useDiagramByRoute(detail?.groupName ?? selectedRow?.groupName, detail?.routeId);
+
   const totalCount = stats?.totalCount ?? 0;
   const failedCount = stats?.failedCount ?? 0;
   const successRate = totalCount > 0 ? ((totalCount - failedCount) / totalCount * 100) : 100;