It works-ish

vite.preload.config.ts

@@ -0,0 +1,13 @@
+import { defineConfig } from "vite";
+
+// https://vitejs.dev/config
+export default defineConfig({
+  build: {
+    outDir: ".vite/build",
+    lib: {
+      formats: ["es"],
+      entry: "electron/preload.ts",
+      fileName: "preload",
+    },
+  },
+});