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/lib/base.sh

@@ -215,6 +215,21 @@ prompt_value() {
   fi
 }
 
+# Show long output a screen at a time.
+#
+# Only when there is a terminal to page on: with output redirected or piped —
+# a transcript, a log, the test harness — it has to come through whole, and a
+# pager would either block or mangle it. `more` rather than `less` because it
+# exits at the end of the file instead of sitting there waiting to be quit,
+# which is what you want for something you asked to read once.
+page() {
+  if [[ -t 1 ]] && command -v more &>/dev/null; then
+    more
+  else
+    cat
+  fi
+}
+
 # Ask before acting. Every section that changes the machine goes through this, so
 # a run is a sequence of things you agreed to rather than a wall of output you
 # read afterwards to find out what happened.
@@ -255,7 +270,7 @@ confirm() {
       "?")
         if [[ -n "$help_fn" ]]; then
           echo ""
-          "$help_fn"
+          "$help_fn" | page
           echo ""
         else
           warn "Answer y or n."

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
             ;;