v1.6.4

Desktop Sync gives you an address a computer can reach, and a link you can copy.

With mobile data on alongside Wi-Fi, the link could name the carrier's address
instead of the phone's. The relay was listening correctly the whole time, so
everything looked right except the one address you were handed, and the browser
simply timed out. It asks the system which network is Wi-Fi now rather than
taking whichever address it found first — and where there is no such network it
says so instead of offering one that cannot work.

The link can be copied. It had to be read off the phone and typed into a
computer, and the token was drawn from an alphabet holding both l and I and 1.
New links avoid every character that can be mistaken for another, and a link
typed by hand is no longer refused for its capitals. Existing links keep
working; Reset Desktop Sync link issues one in the new alphabet.

On a phone with two SIMs, a conversation now says which one the newest message
went out on. It was marked only where the SIM changed, which on a thread that
never changes meant a single mark at the very top, far from anything you were
looking at.

Thanks to those who reported the address bug and asked for the rest.

Full Changelog: v1.6.3...v1.6.4