handle() is dispatched via `void`, so a throw before its try/catch is an
unhandled rejection on a LAN-facing server. A request target the HTTP
parser accepts but the WHATWG URL parser rejects (unterminated IPv6 host
like //[::1) threw at new URL() and hung/killed the process. Parse inside
a guard and answer 400. Mutation-checked: the test times out with an
unhandled error before the fix, passes after.
