fix: avoid duplicate world map background loads

.superpowers/sdd/2026-08-18-first-visible-vertical-slice/task-9-report.md

@@ -31,6 +31,7 @@ The reference screenshots were inspected but are not shipped or referenced by th
 - The decision panel now occupies normal document flow below the map scene, reserving a non-overlapping zone at desktop and narrow breakpoints.
 - The original delivered PNGs remain untouched. A deterministic local System.Drawing JPEG conversion (quality 86, high-quality bicubic) provides runtime derivatives: `map_ashen_realm-1440.jpg` (1440x810, 233,778 B), `Suedtor-960.jpg` (960x540, 94,286 B), and `Aschestrasse-960.jpg` (960x540, 93,277 B). The WorldPage and ContextPanel prefer these derivatives while retaining each server artwork path as the `<img>` fallback.
 - The load error is exposed as an alert and its retry control is covered by a store-load regression test.
+- The map no longer declares the runtime JPEG and original PNG as comma-separated background layers. It uses the original PNG as the classic CSS fallback and, where `image-set` with JPEG is supported, replaces it with one runtime JPEG candidate. The WorldPage regression test verifies there is no inline multi-layer binding or `mapBackground` source left to reintroduce the double load.
 
 ## Verification
 
@@ -43,6 +44,7 @@ The reference screenshots were inspected but are not shipped or referenced by th
 - Review full web suite: 23/23 pass.
 - Affected API seed test: 2/2 pass.
 - Both review builds (`npm run build:web`, `npm run build:api`) pass.
+- Review-fix round 2: focused WorldPage test 7/7 pass; full web suite and web build re-run after the fallback change.
 
 ## Remaining concern
 

apps/web/src/app/features/world/world-page.component.html

@@ -1,10 +1,6 @@
 <section class="world-page" aria-label="Weltansicht">
   @if (worldStore.currentLocation(); as location) {
-    <section
-      class="world-page__scene"
-      [style.background-image]="mapBackground"
-      [attr.aria-label]="'Weltkarte bei ' + location.name"
-    >
+    <section class="world-page__scene" [attr.aria-label]="'Weltkarte bei ' + location.name">
       <div class="world-page__atmosphere" aria-hidden="true"></div>
       <p class="world-page__location-title">{{ location.name }}</p>
 

apps/web/src/app/features/world/world-page.component.scss

@@ -15,12 +15,25 @@
   overflow: hidden;
   border: 1px solid var(--ar-border);
   background-color: #151718;
+  background-image: url('/images/backgrounds/map_ashen_realm.png');
   background-position: center;
   background-repeat: no-repeat;
   background-size: cover;
   box-shadow: var(--ar-shadow-raised);
 }
 
+@supports (
+  background-image: image-set(
+      url('/images/backgrounds/runtime/map_ashen_realm-1440.jpg') type('image/jpeg') 1x
+    )
+) {
+  .world-page__scene {
+    background-image: image-set(
+      url('/images/backgrounds/runtime/map_ashen_realm-1440.jpg') type('image/jpeg') 1x
+    );
+  }
+}
+
 .world-page__scene::after {
   position: absolute;
   z-index: -1;

apps/web/src/app/features/world/world-page.component.spec.ts

@@ -122,9 +122,8 @@ describe('WorldPageComponent', () => {
     expect(
       element.querySelector('.world-page__node--burned-road [data-location-key="burned-road"]'),
     ).not.toBeNull();
-    expect(element.querySelector('.world-page__scene')?.getAttribute('style')).toContain(
-      'map_ashen_realm-1440.jpg',
-    );
+    expect(element.querySelector('.world-page__scene')?.getAttribute('style')).toBeNull();
+    expect(fixture.componentInstance).not.toHaveProperty('mapBackground');
 
     store.currentLocation.set(burnedRoad);
     fixture.detectChanges();

apps/web/src/app/features/world/world-page.component.ts

@@ -12,8 +12,6 @@ import { WorldStore } from './world.store';
 })
 export class WorldPageComponent implements OnInit {
   protected readonly worldStore = inject(WorldStore);
-  protected readonly mapBackground =
-    "url('/images/backgrounds/runtime/map_ashen_realm-1440.jpg'), url('/images/backgrounds/map_ashen_realm.png')";
 
   ngOnInit(): void {
     void this.worldStore.load();