fix: improve duration formatting (Xm Ys) and truncate exchange IDs

- formatDuration and formatDurationShort now show Xm Ys for durations >= 60s (e.g. "5m 21s" instead of "321s") and 1 decimal for 1-60s range ("6.7s" instead of "6.70s")
- Exchange ID column shows last 8 chars with ellipsis prefix; full ID on hover, copies to clipboard on click

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ui/src/pages/DashboardTab/DashboardL3.tsx

@@ -392,7 +392,7 @@ export default function DashboardL3() {
 
       {/* Process Diagram with Latency Heatmap */}
       {appId && routeId && (
-        <div className={styles.diagramSection}>
+        <div className={`${tableStyles.tableSection} ${styles.diagramHeight}`}>
           <ProcessDiagram
             application={appId}
             routeId={routeId}
@@ -421,7 +421,7 @@ export default function DashboardL3() {
 
       {/* Top 5 Errors — hidden if empty */}
       {errorRows.length > 0 && (
-        <div className={styles.errorsSection}>
+        <div className={tableStyles.tableSection}>
           <div className={tableStyles.tableHeader}>
             <span className={tableStyles.tableTitle}>Top 5 Errors</span>
             <Badge label={`${errorRows.length}`} color="error" />