Handle stale frontend assets and harden worker startup

server/_core/static.ts

@@ -13,9 +13,17 @@ export function serveStatic(app: Express) {
     );
   }
 
-  app.use(express.static(distPath));
+  app.use(express.static(distPath, { index: false }));
+
+  app.use("*", (req, res) => {
+    // Missing files under /assets or any path with an extension must return 404.
+    // Falling back to index.html causes browsers to report MIME errors on stale chunks.
+    const requestPath = req.originalUrl.split("?")[0];
+    if (path.extname(requestPath)) {
+      res.status(404).type("text/plain").send("Not found");
+      return;
+    }
 
-  app.use("*", (_req, res) => {
     res.sendFile(path.resolve(distPath, "index.html"));
   });
 }