Fires a no-cors fetch to a Cloudflare endpoint with HTTP/3 advertised via DNS HTTPS records. Pair with an EXTRACT_NETWORK workflow on the same URL to confirm whether our capture stack sees HTTP/3 traffic.
The page can't read the trace body itself (no-cors → opaque response), but tshark on the worker can decrypt and emit the response body via the EXTRACT_NETWORK pipeline. The trace payload includes an http= line revealing which protocol Chrome actually used.