Faster shopfloor-setup sync, prompt spacing, XP-era test client

- Deploy shopfloor-setup with rsync instead of the copy module: the
  ~4 GB tree took about 4 minutes on every re-run because copy checksums
  each file. rsync transfers only changes; changed only when it did.
- iPXE drops a trailing space, so 'Machine number:' ran into the typed
  digits. The space now comes from a hex 20 setting.
- tests/vm: pxetest-xp is a permanent client (SeaBIOS, qemu32 32-bit CPU,
  rtl8139, 1 GiB, IDE disk) for the i686 Clonezilla path; start.sh xp.
  Only one client may run at a time across all three.

tests/vm/common.sh

@@ -52,6 +52,14 @@ CLIENT_MAC="52:54:00:9e:10:03"          # on pxetest-imaging only
 CLIENT2_VM="pxetest-client-nosb"
 CLIENT2_DISK_VOL="pxetest-client-nosb.qcow2"
 CLIENT2_MAC="52:54:00:9e:10:04"         # on pxetest-imaging only
+# Third client: a 15-20-year-old XP/Win7-era PC. Legacy BIOS (SeaBIOS),
+# 32-bit only CPU (qemu32: no long mode, so the menu picks the i686
+# Clonezilla), rtl8139 NIC, IDE disk, 1 GiB.
+CLIENT3_VM="pxetest-xp"
+CLIENT3_DISK_VOL="pxetest-xp.qcow2"
+CLIENT3_MAC="52:54:00:9e:10:05"         # on pxetest-imaging only
+CLIENT3_MEM_MIB="${CLIENT3_MEM_MIB:-1024}"
+ALL_CLIENTS=("pxetest-client" "pxetest-client-nosb" "pxetest-xp")
 
 log() { printf '[pxetest] %s\n' "$*"; }
 die() { printf '[pxetest] ERROR: %s\n' "$*" >&2; exit 1; }