@v5x/web normalizes thrown values into V5WebError. 
import { createV5Client } from "@v5x/web";

const client = createV5Client();

if (!(await client.connect())) {
  const { error } = client.getSnapshot();
  console.log(error?.code);
}
Each error has a stable code, a message, and an optional cause. The first milestone reports support, connect, disconnect, and refresh errors. Higher-level workflow errors for files, programs, screenshots, and key-value settings will be added with those workflows. When Web Serial is unavailable, the snapshot status is unsupported and unavailableReason is web-serial-unavailable.