page the ? output

The long answer is now well past a screen, so it scrolls the question off the top
and the reader lands at a prompt having lost what they were choosing between.
Piped through a pager, so it is read a screen at a time and the menu is redrawn
underneath it afterwards.

`more` rather than `less`: it exits at the end of the file instead of sitting
there waiting to be quit, which is right for something asked for once.

Only when stdout is a terminal. Redirected or piped — a transcript, a log, the
test harness — it comes through whole, since a pager there either blocks or
mangles the output.

Applied to confirm()'s help hook as well, so every ? in the script pages, not
just this one.

Verified both ways: driven through a pty it shows --More--, and with output
piped all four help sections come through in full.

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

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

@@ -470,7 +470,7 @@ if ! skip; then
           3) TS_PLANE="tailscale" ;;
           "?")
             echo ""
-            tailscale_networks_help
+            tailscale_networks_help | page
             echo ""
             tailscale_network_menu
             ;;