Fail fast on missing terrain assets and recover empty renders

scripts/setup.mjs

@@ -7,6 +7,8 @@ await mkdir(".data", { recursive: true });
 await mkdir("public/generated", { recursive: true });
 await mkdir("public/tools/mod", { recursive: true });
 await mkdir("public/tools/plugin", { recursive: true });
+// Prepare terrain assets even if browser installation subsequently fails.
+await prepareAssets();
 await new Promise((resolve, reject) => {
   const p = spawn(
     process.execPath,
@@ -19,7 +21,6 @@ await new Promise((resolve, reject) => {
       : reject(new Error(`Chromium installation exited ${code}`)),
   );
 });
-await prepareAssets();
 process.loadEnvFile(".env.local");
 const configured = Boolean(
   process.env.NEXT_PUBLIC_SUPABASE_URL &&