docs: qualify what an invitation link changes about the code

The security claims table, §3.4's property 2, the protocol's stated
limits, the quickstart and the user guide's defaults now say where a
link's code differs: bound to its account only when redeemed, and held
by the hub when the inviter asks it to mail.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/docs/QUICKSTART.md b/docs/QUICKSTART.md
index 4da1eff..bf6cc80 100644
--- a/docs/QUICKSTART.md
+++ b/docs/QUICKSTART.md
@@ -318,6 +318,11 @@ Send that code however you normally talk to them — message, mail, out loud. It
 works once, for that account only, for that group only, and the hub never sees
 it. You do not need to be online when they use it.
 
+Someone with no account yet gets a link instead, bound to their e-mail address:
+`meshbay-node member invite alice@example.org --link`. They open it, register
+with that address, and land in the group without typing a code
+([`USERGUIDE.md` §7](USERGUIDE.md#7-managing-people)).
+
 You can do the same thing from the **Members** tab of the group, from the
 browser you paired in Step 8. There, **Send the invitation by e-mail** is ticked
 by default and has the hub mail the code for you — which means the hub reads it.