refactor: separate standalone Vite wiring and provider middleware

server/standalone/vite.config.js

@@ -0,0 +1,21 @@
+import { fileURLToPath } from 'node:url';
+import { defineConfig, loadEnv } from 'vite';
+import { createBrowserViteConfig } from '../../build/vite.js';
+import { localProviderPlugins } from '../providers/local.js';
+
+const root = fileURLToPath(new URL('../../', import.meta.url));
+
+/** Load this checkout's configuration and attach its local provider middleware. */
+export default defineConfig(({ mode }) => {
+  const loaded = loadEnv(mode, root, '');
+  for (const [key, value] of Object.entries(loaded)) {
+    if (process.env[key] === undefined) process.env[key] = value;
+  }
+  return createBrowserViteConfig({
+    plugins: localProviderPlugins(),
+    googleApiKey: process.env.GOOGLE_MAPS_API_KEY,
+    cesiumToken: process.env.CESIUM_ION_TOKEN,
+    host: process.env.HOST,
+    port: process.env.PORT,
+  });
+});