An address is parsed from input nobody authenticated: typed, pasted,
scanned from a code somebody else printed, and — worst — read out of a
sealed envelope written by a stranger on another relay. So the refusals
matter more than the successes.
Written to mirror the Swift cases one for one, because two
implementations that disagree about which strings are addresses open two
threads for one person on one side and none on the other, and nothing
about either engine's own tests would show it.
It found one on the first run, in the other direction: Swift's decoder
splits on the first `@` with `maxSplits: 1` and then refuses `/` and `:`
but not `@` — so `fn1abc@a@b.example.com` parsed as a relay of
`a@b.example.com`, a "hostname" no host is called. Fixed there.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
