add the offscale line, and fix a set -e bug the test exposed

The menu is one function now rather than being written out twice — it is shown
again after ? prints the long answer — and option 1 carries your line: offscale is
just tailscale and headscale, with our own sugar on top.

The bug it surfaced is the more useful half. load_answers used

    [[ -z "${MACHINE_ROLE:-}" ]] && MACHINE_ROLE="$value"

as the last statement in a while-read loop body. When the variable is already set
the test is false, the compound returns non-zero, and as the final statement in a
loop body under `set -e` that ends the script. The failure is silent about its
cause: the trap prints "Step: unknown" and a line number inside the library,
before pre-flight has run.

It needed both conditions to appear — an answers file on disk AND the variables
already set in the environment — which is why every earlier test missed it and
running with env overrides hit it immediately. Written as if/then now, and the
other lib files scanned for the same shape.

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

scripts/setup/machine-setup/lib/base.sh

@@ -120,10 +120,17 @@ load_answers() {
     [[ "$key" =~ ^[A-Z_]+$ ]] || continue
     [[ -n "$value" ]] || continue
     # The environment wins over what was saved.
+    #
+    # Written as if/then rather than `[[ … ]] && assign`. That form returns
+    # non-zero when the test is false, and as the last statement in a loop body
+    # under `set -e` it takes the whole script down — which is exactly what
+    # happened the first time this ran with the variables already set in the
+    # environment: the file loaded fine, every value was already present, and the
+    # run died at "Step: unknown" before pre-flight.
     case "$key" in
-      MACHINE_ROLE) [[ -z "${MACHINE_ROLE:-}" ]] && MACHINE_ROLE="$value" ;;
-      SETUP_USERNAME) [[ -z "${SETUP_USERNAME:-}" ]] && SETUP_USERNAME="$value" ;;
-      OFFICER_ROOT) [[ -z "${OFFICER_ROOT:-}" ]] && OFFICER_ROOT="$value" ;;
+      MACHINE_ROLE) if [[ -z "${MACHINE_ROLE:-}" ]]; then MACHINE_ROLE="$value"; fi ;;
+      SETUP_USERNAME) if [[ -z "${SETUP_USERNAME:-}" ]]; then SETUP_USERNAME="$value"; fi ;;
+      OFFICER_ROOT) if [[ -z "${OFFICER_ROOT:-}" ]]; then OFFICER_ROOT="$value"; fi ;;
     esac
   done <"$ANSWERS_FILE"
 }

scripts/setup/machine-setup/lib/tailscale.sh

@@ -55,6 +55,20 @@ tailscale_help() {
   echo "     lock you out of the machine, so there is always a second way in."
 }
 
+# The menu itself, in a function because it is shown twice — once to ask, and
+# again after ? has printed the long answer, so the reader is not dropped back at
+# a bare prompt having forgotten what the options were.
+tailscale_network_menu() {
+  info "Which network should this machine join?"
+  echo ""
+  echo "     [1] set up your own network        (offscale)"
+  echo "         offscale is just tailscale and headscale, with our own sugar on top"
+  echo "     [2] use a network you already run  (headscale, offscale)"
+  echo "     [3] the easy route                 (tailscale.com)"
+  echo "     [?] what are tailscale, headscale and offscale?"
+  echo ""
+}
+
 # The long answer, printed when somebody types ?. Covers all three names,
 # because the menu offers all three and two of them are not words anyone outside
 # this project would know.