A hosted game gets an 8-character join code (Crockford base 32) besides
its invite link, shown under the lobby's buttons. On the system link list,
X opens the game's keyboard to type a code in; the code's topic and key
come from a slow PBKDF2 derivation, the host answers an ask on that topic
through the signalling brokers with its invite sealed with the key, and
the joiner joins as with the link. Codes in join_link.txt work too.
Also: the clipboard text last seen is kept from run to run, so a run's
own invite is not joined again at the next start; in menus a held stick
repeats after 350 ms and then every 90 ms, and its threshold is 70%.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>