installer: tolerate missing tty in offline finalizer

test/offline-finalizer-bootstrap-test.sh

@@ -0,0 +1,37 @@
+#!/usr/bin/env bash
+# Ensure the offline/chroot finalizer can source helpers with no controlling tty.
+set -euo pipefail
+
+ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+
+output="$({
+  setsid -w bash -c '
+    set -eEo pipefail
+    export OMARCHY_INSTALL="$1/install"
+    export OMARCHY_PATH="${OMARCHY_TEST_OMARCHY_PATH:-/usr/share/omarchy}"
+    export OMARCHY_INSTALL_MODE=offline
+    export OMARCHY_CHROOT_FINALIZER=1
+    export HOME="$(mktemp -d)"
+    export USER=ryan
+
+    source "$OMARCHY_INSTALL/helpers/mode.sh"
+    detect_install_mode
+    export_legacy_mode_flags
+    source "$OMARCHY_INSTALL/helpers/all.sh"
+    echo helpers-loaded
+  ' bash "$ROOT" </dev/null
+} 2>&1)"
+
+printf '%s\n' "$output"
+
+if [[ $output != *helpers-loaded* ]]; then
+  echo "expected helpers-loaded marker" >&2
+  exit 1
+fi
+
+if [[ $output == *$'\033[?25h'* ]]; then
+  echo "offline finalizer helper bootstrap leaked cursor escape" >&2
+  exit 1
+fi
+
+echo "offline finalizer bootstrap test passed"