fix carplace page

apps/carplace/next.config.js

@@ -3,8 +3,15 @@
 const { buildSecurityHeaders, normalizeAssetPrefix } = require('../../config/nextSecurityHeaders')
 
 const CARPLACE_ASSET_PREFIX = '/carplace'
+// In local development the homepage app serves /carplace from port 3000 while
+// the Carplace dev server runs on port 3004. Emit absolute chunk/HMR URLs so
+// the browser asks the Carplace server for its own assets instead of the
+// homepage server.
+const defaultCarplaceAssetPrefix = process.env.NODE_ENV !== 'production'
+  ? 'http://localhost:3004'
+  : CARPLACE_ASSET_PREFIX
 const carplaceAssetPrefix = normalizeAssetPrefix(
-  process.env.CARPLACE_ASSET_PREFIX ?? (process.env.NODE_ENV === 'production' ? CARPLACE_ASSET_PREFIX : undefined),
+  process.env.CARPLACE_ASSET_PREFIX ?? defaultCarplaceAssetPrefix,
   CARPLACE_ASSET_PREFIX,
 )
 const securityHeaders = buildSecurityHeaders({ assetSources: [carplaceAssetPrefix] })