fix: Cmd-K exchange selection reads exchangeId from URL params

ExchangesPage ignored the exchangeId URL parameter, so selecting an
exchange from the command palette navigated to the right URL but never
displayed the execution overlay. Now derives selection from URL params
as fallback, and LayoutShell passes selectedExchange in state for
exchange/attribute results.

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

ui/src/components/LayoutShell.tsx

@@ -210,7 +210,21 @@ function LayoutContent() {
 
   const handlePaletteSelect = useCallback((result: any) => {
     if (result.path) {
-      navigate(result.path, { state: result.path ? { sidebarReveal: result.path } : undefined });
+      const state: Record<string, unknown> = { sidebarReveal: result.path };
+
+      // For exchange/attribute results, pass selectedExchange in state
+      if (result.category === 'exchange' || result.category === 'attribute') {
+        const parts = result.path.split('/').filter(Boolean);
+        if (parts.length === 4 && parts[0] === 'exchanges') {
+          state.selectedExchange = {
+            executionId: parts[3],
+            applicationName: parts[1],
+            routeId: parts[2],
+          };
+        }
+      }
+
+      navigate(result.path, { state });
     }
     setPaletteOpen(false);
   }, [navigate, setPaletteOpen]);