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>

cameleer3-server-core/src/main/java/com/cameleer3/server/core/detail/DetailService.java

@@ -20,6 +20,7 @@ public class DetailService {
                     List<ProcessorNode> roots = buildTree(processors);
                     return new ExecutionDetail(
                             exec.executionId(), exec.routeId(), exec.agentId(),
+                            exec.groupName(),
                             exec.status(), exec.startTime(), exec.endTime(),
                             exec.durationMs() != null ? exec.durationMs() : 0L,
                             exec.correlationId(), exec.exchangeId(),

cameleer3-server-core/src/main/java/com/cameleer3/server/core/detail/ExecutionDetail.java

@@ -27,6 +27,7 @@ public record ExecutionDetail(
         String executionId,
         String routeId,
         String agentId,
+        String groupName,
         String status,
         Instant startTime,
         Instant endTime,