frame the public server as common to all three, not a cost of offscale

"offscale runs on a publicly reachable server" read as a demand offscale makes
and the easy route does not. It is not. Tailscale's coordination server is
publicly reachable too — they run it for you, and that is the entire difference
between option 3 and hosting it yourself.

Said that way round, the requirement stops being a reason not to self-host and
becomes what self-hosting means. Same sentence in all three places: the menu
entry, the branch taken when 1 is chosen, and the long answer.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

scripts/setup/machine-setup/machine-setup.sh

@@ -457,9 +457,10 @@ if ! skip; then
             # what to say, not what to do.
             if [[ "$TS_PLANE_CHOICE" == "1" ]]; then
               echo ""
-              echo "     offscale runs on a publicly reachable server of its own — not"
-              echo "     this machine, and not behind a home router. Work through the"
-              echo "     whole setup there first:"
+              echo "     offscale — just like headscale, and just like Tailscale's own"
+              echo "     service — needs to run on a publicly reachable server of its"
+              echo "     own. Not this machine, and not behind a home router. Work"
+              echo "     through the whole setup there first:"
               echo ""
               echo "       https://officer.dev/infrastructure/offscale.html#install"
               echo ""