fix: use absolute asset paths and prevent route-level runtime navigation

Change vite base from './' to '/' so asset paths are absolute. With
relative paths, direct navigation to multi-segment URLs like
/runtime/app/instance resolved assets to /runtime/assets/ which 404'd.

Also fix sidebar navigation: clicking a route while on the runtime tab
no longer navigates to /runtime/{appId}/{routeId} (which the runtime
page interprets as an instanceId). It stays at /runtime/{appId}.

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

ui/src/components/LayoutShell.tsx

@@ -640,8 +640,10 @@ function LayoutContent() {
     if (appMatch) {
       const [, sAppId, sRouteId] = appMatch;
       if (scope.tab === 'apps') {
-        // Deployments tab: navigate to /apps/:appId
         navigate(`/apps/${sAppId}`, { state });
+      } else if (scope.tab === 'runtime') {
+        // Runtime tab has no route-level view — stay at app level
+        navigate(`/runtime/${sAppId}`, { state });
       } else {
         navigate(sRouteId ? `/${scope.tab}/${sAppId}/${sRouteId}` : `/${scope.tab}/${sAppId}`, { state });
       }
@@ -653,6 +655,8 @@ function LayoutContent() {
       const [, sAppId, sRouteId] = exchangeMatch;
       if (scope.tab === 'apps') {
         navigate(`/apps/${sAppId}`, { state });
+      } else if (scope.tab === 'runtime') {
+        navigate(`/runtime/${sAppId}`, { state });
       } else {
         navigate(sRouteId ? `/${scope.tab}/${sAppId}/${sRouteId}` : `/${scope.tab}/${sAppId}`, { state });
       }

ui/vite.config.ts

@@ -27,7 +27,7 @@ export default defineConfig({
   optimizeDeps: {
     include: ['swagger-ui-dist/swagger-ui-bundle'],
   },
-  base: './',
+  base: '/',
   build: {
     outDir: 'dist',
   },