fix(simulation): keep runtime stable on settings save

apps/control-station/src/components/simulation/SimulationViewport.tsx

@@ -62,6 +62,7 @@ export function SimulationViewport({
     project.viewerSettings.camera.invertVertical,
   );
   const [settingsError, setSettingsError] = useState<string | null>(null);
+  const worldManifestRevision = JSON.stringify(project.worldManifest);
 
   useEffect(() => {
     const settings = project.viewerSettings;
@@ -142,7 +143,10 @@ export function SimulationViewport({
       runtime.dispose();
       runtimeRef.current = null;
     };
-  }, [project.projectId, project.worldManifest]);
+  // Saving viewer preferences returns a fresh project object. Restart the GPU
+  // runtime only when the manifest content changes, not when its object identity
+  // changes after an otherwise unrelated settings PUT.
+  }, [project.projectId, worldManifestRevision]);
 
   const collisionAvailable = project.worldManifest?.collision.available ?? false;
   const commitViewerSettings = (settings: SimulationViewerSettings) => {