fix bun dev not starting correctly.

src/index.ts

@@ -178,7 +178,15 @@ async function developmentServeOptions(): Promise<ServeOptions> {
   const scriptHeaders = { "Content-Type": "text/javascript; charset=utf-8" };
 
   return {
-    async fetch(request) {
+    routes: {
+      // The HTML import is an HTMLBundle, which Bun only serves as a route
+      // value — returning it from fetch() throws "Expected a Response object".
+      "/": index,
+    },
+
+    // Fallback for everything the route table doesn't match, including
+    // subpath-proxied requests (/proxy/api/..., /proxy/sw.js, ...).
+    async fetch(request, server) {
       const url = new URL(request.url);
       const pathname = url.pathname;
 
@@ -204,9 +212,10 @@ async function developmentServeOptions(): Promise<ServeOptions> {
         return serveOrtFile(ORT_DIST, ortMatch[1]);
       }
 
-      // Serve the bundled React app for all other routes.
-      // In development, this is a special Response object from Bun's HTML bundler.
-      return index;
+      // SPA fallback: unknown navigations (including subpath ones) get the
+      // app shell. The HTMLBundle itself can only live in `routes`, so
+      // re-enter the server at "/" to let it produce the dev-bundled HTML.
+      return fetch(new URL("/", server.url));
     },
 
     development: {