fix: stop getty@tty1 before first-boot setup service to prevent SIGHUP kill

Conflicts=getty@tty1 ensures systemd releases TTY1 before kiosk-setup
runs interactively. Also add partman/choose_partition select finish to
preseed so disk write confirmation is fully automated.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

preseed.cfg

@@ -38,13 +38,16 @@ d-i passwd/root-password-again password kiosk
 # Handles /dev/sda, /dev/nvme0n1, /dev/vda, etc.
 d-i preseed/early_command string \
   DISK=$(ls /sys/block/ | grep -Ev '^(loop|sr|fd|ram)' | head -1); \
-  debconf-set partman-auto/disk "/dev/$DISK"; \
-  debconf-set grub-installer/bootdev "/dev/$DISK"; \
-  ETH=$(ls /sys/class/net/ | grep -E '^(eth|en)' | head -1); \
-  [ -n "$ETH" ] && debconf-set netcfg/choose_interface "$ETH"
+  debconf-set partman-auto/disk "/dev/$DISK" || true; \
+  debconf-set grub-installer/bootdev "/dev/$DISK" || true; \
+  ETH=$(ls /sys/class/net/ 2>/dev/null | grep -E '^(eth|en)' | head -1 || true); \
+  if [ -n "$ETH" ]; then debconf-set netcfg/choose_interface "$ETH" || true; fi; \
+  true
 
 d-i partman-auto/method string regular
 d-i partman-auto/choose_recipe select atomic
+d-i partman-partitioning/confirm_write_new_label boolean true
+d-i partman/choose_partition select finish
 d-i partman/confirm_write_new_label boolean true
 d-i partman/confirm boolean true
 d-i partman/confirm_nooverwrite boolean true