Node's network-family auto-selection gives each resolved address a short
attempt timeout. On hosts where IPv6 is unreachable, a slow IPv4 handshake
is abandoned for the IPv6 address, which fails at once, and the request
reports only `fetch failed`. Retry such failures once with a single IPv4
connection within the same deadline, and log the per-address connection
errors (never the keyed URL). Node 26 wraps the AggregateError one level
deeper, so both shapes are recognised.
Fixes#68
jeffblakely