Fix surface filtering in user settings and welcome surface

The /api/v1/surfaces endpoint doesn't return source field, so
filter by route pattern (/s/ prefix) instead of source !== 'core'.

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

src/js/sw/surfaces/settings/general.js

@@ -18,7 +18,7 @@ export function GeneralSection() {
                 ]);
                 const sObj = s || {};
                 setDefaultSurface(sObj.default_surface || '');
-                setSurfaces((surfList || []).filter(s => s.source !== 'core' && s.enabled));
+                setSurfaces((surfList || []).filter(s => s.route?.startsWith('/s/')));
             } catch (e) {
                 console.warn('[settings/general] Load failed:', e.message);
             }

src/js/sw/surfaces/welcome/index.js

@@ -16,7 +16,7 @@ function WelcomeSurface() {
 
     useEffect(() => {
         sw.api.get('/api/v1/surfaces').then(list => {
-            setSurfaces((list || []).filter(s => s.source !== 'core'));
+            setSurfaces((list || []).filter(s => s.route?.startsWith('/s/')));
         }).catch(() => {});
     }, []);