feat(ui): add draggable splitter between search results and diagram panel

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

@@ -1,6 +1,5 @@
 .splitView {
-  display: grid;
+  display: flex;
-  grid-template-columns: 1fr 1fr;
   height: 100%;
   overflow: hidden;
 }
@@ -8,14 +7,30 @@
 .leftPanel {
   overflow: auto;
   height: 100%;
-  border-right: 1px solid var(--border);
+  flex-shrink: 0;
+}
+
+.splitter {
+  width: 5px;
+  flex-shrink: 0;
+  cursor: col-resize;
+  background: var(--border);
+  transition: background 0.15s;
+  touch-action: none;
+}
+
+.splitter:hover,
+.splitter:active {
+  background: var(--amber);
 }
 
 .rightPanel {
+  flex: 1;
   display: flex;
   flex-direction: column;
   overflow: hidden;
   height: 100%;
+  min-width: 0;
 }
 
 .emptyRight {

ui/src/pages/Exchanges/ExchangesPage.tsx

@@ -1,4 +1,4 @@
-import { useState, useMemo, useCallback } from 'react';
+import { useState, useMemo, useCallback, useRef } from 'react';
 import { useParams } from 'react-router';
 import { useGlobalFilters } from '@cameleer/design-system';
 import { useExecutionDetail } from '../../api/queries/executions';
@@ -22,14 +22,48 @@ export default function ExchangesPage() {
     return <Dashboard />;
   }
 
-  // Route scoped: 50:50 split — Dashboard table on left, diagram on right
+  // Route scoped: resizable split — Dashboard table on left, diagram on right
+  return <SplitExchangeView appId={appId!} routeId={routeId} exchangeId={exchangeId} />;
+}
+
+// ─── Resizable split view ───────────────────────────────────────────────────
+
+interface SplitExchangeViewProps {
+  appId: string;
+  routeId: string;
+  exchangeId?: string;
+}
+
+function SplitExchangeView({ appId, routeId, exchangeId }: SplitExchangeViewProps) {
+  const [splitPercent, setSplitPercent] = useState(50);
+  const containerRef = useRef<HTMLDivElement>(null);
+
+  const handleSplitterDown = useCallback((e: React.PointerEvent) => {
+    e.currentTarget.setPointerCapture(e.pointerId);
+    const container = containerRef.current;
+    if (!container) return;
+    const onMove = (me: PointerEvent) => {
+      const rect = container.getBoundingClientRect();
+      const x = me.clientX - rect.left;
+      const pct = Math.min(80, Math.max(20, (x / rect.width) * 100));
+      setSplitPercent(pct);
+    };
+    const onUp = () => {
+      document.removeEventListener('pointermove', onMove);
+      document.removeEventListener('pointerup', onUp);
+    };
+    document.addEventListener('pointermove', onMove);
+    document.addEventListener('pointerup', onUp);
+  }, []);
+
   return (
-    <div className={styles.splitView}>
+    <div ref={containerRef} className={styles.splitView}>
-      <div className={styles.leftPanel}>
+      <div className={styles.leftPanel} style={{ width: `${splitPercent}%` }}>
         <Dashboard />
       </div>
-      <div className={styles.rightPanel}>
+      <div className={styles.splitter} onPointerDown={handleSplitterDown} />
-        <DiagramPanel appId={appId!} routeId={routeId} exchangeId={exchangeId} />
+      <div className={styles.rightPanel} style={{ width: `${100 - splitPercent}%` }}>
+        <DiagramPanel appId={appId} routeId={routeId} exchangeId={exchangeId} />
       </div>
     </div>
   );
@@ -48,13 +82,9 @@ function DiagramPanel({ appId, routeId, exchangeId }: DiagramPanelProps) {
   const timeFrom = timeRange.start.toISOString();
   const timeTo = timeRange.end.toISOString();
 
-  // Fetch execution detail if an exchange is selected
   const { data: detail } = useExecutionDetail(exchangeId ?? null);
-
-  // Fetch diagram for topology-only view
   const diagramQuery = useDiagramByRoute(appId, routeId);
 
-  // Known route IDs for drill-down
   const { data: catalog } = useRouteCatalog(timeFrom, timeTo);
   const knownRouteIds = useMemo(() => {
     const ids = new Set<string>();
@@ -68,7 +98,6 @@ function DiagramPanel({ appId, routeId, exchangeId }: DiagramPanelProps) {
     return ids;
   }, [catalog]);
 
-  // If exchange selected: show header + ExecutionDiagram
   if (exchangeId && detail) {
     return (
       <>
@@ -82,7 +111,6 @@ function DiagramPanel({ appId, routeId, exchangeId }: DiagramPanelProps) {
     );
   }
 
-  // No exchange: show topology-only ProcessDiagram
   if (diagramQuery.data) {
     return (
       <ProcessDiagram