fix: Config tab sidebar navigation stays on config for app and route clicks

When on Config tab: clicking an app navigates to /config/:appId (shows
that app's config with detail panel). Clicking a route navigates to
/config/:appId (same app config, since config is per-app not per-route).
Clicking Applications header navigates to /config (all apps table).

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

ui/src/components/LayoutShell.tsx

@@ -604,9 +604,12 @@ function LayoutContent() {
     const appMatch = path.match(/^\/apps\/([^/]+)(?:\/(.+))?$/);
     if (appMatch) {
       const [, sAppId, sRouteId] = appMatch;
-      // Config tab only supports /config/:appId — fall back to exchanges for route-level
-      const tab = (scope.tab === 'config' && sRouteId) ? 'exchanges' : scope.tab;
-      navigate(sRouteId ? `/${tab}/${sAppId}/${sRouteId}` : `/${tab}/${sAppId}`, { state });
+      if (scope.tab === 'config') {
+        // Config tab: always navigate to /config/:appId (route click → same app config)
+        navigate(`/config/${sAppId}`, { state });
+      } else {
+        navigate(sRouteId ? `/${scope.tab}/${sAppId}/${sRouteId}` : `/${scope.tab}/${sAppId}`, { state });
+      }
       return;
     }