ShouldBindLoopbackQUIC: a listener on 127.0.0.1 at port 0 serves a
client through 127.0.0.1 and refuses, within 3 s of a 6 s handshake
timeout, one through this host's first non-loopback IPv4 address (found
with getifaddrs; that half is skipped with a line saying so when there
is none) and one through ::1; only the served connection reaches
connectCallback. A listener on ::1 serves ::1 and refuses 127.0.0.1, and
`localhost` is refused as a bind address.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
