fix(ui): always show correlation section, display message when none found

ui/src/pages/Exchanges/ExchangeHeader.module.css

@@ -180,3 +180,9 @@
   color: var(--text-muted);
   font-size: 9px;
 }
+
+.chainNone {
+  color: var(--text-muted);
+  font-size: 11px;
+  font-style: italic;
+}

ui/src/pages/Exchanges/ExchangeHeader.tsx

@@ -89,11 +89,10 @@ export function ExchangeHeader({ detail }: ExchangeHeaderProps) {
         <span className={styles.duration}>{formatDuration(detail.durationMs)}</span>
       </div>
 
-      {/* Correlation chain — only when multiple correlated exchanges exist */}
+      {/* Correlation chain */}
-      {showChain && (
       <div className={styles.chain}>
         <span className={styles.chainLabel}>Correlated</span>
-          {chain.map((ce: any, i: number) => {
+        {showChain ? chain.map((ce: any, i: number) => {
             const isCurrent = ce.executionId === detail.executionId;
             const variant = statusVariant(ce.status);
             const statusCls =
@@ -119,9 +118,10 @@ export function ExchangeHeader({ detail }: ExchangeHeaderProps) {
                 </button>
               </span>
             );
-          })}
+          }) : (
-        </div>
+            <span className={styles.chainNone}>no correlated exchanges found</span>
           )}
       </div>
+    </div>
   );
 }