feat(setup): USB printer discovery — pick a real /dev/usb device

The kernel numbers usblp nodes by plug/boot order (park-buzi's printer
is lp1); the wizard hardcoded lp0 in labels/default and the admin had to
shell in and `ls /dev/usb`. Now:

- GET /api/setup/usb-printers enumerates /dev/usb/lpN (visible via the
  compose bind-mount) and enriches each with the printer's self-reported
  make/model from sysfs ieee1284_id (readable through Docker's ro /sys).
- The wizard's devicePath becomes a SELECT of printers actually present
  ("/dev/usb/lp1 — Xprinter XP-K200L"): a fresh form preselects the
  first real device; a saved-but-unplugged path stays selectable,
  flagged "saved — not present now"; zero found falls back to free text
  + a check-the-cable hint.
- Transport option label no longer hardcodes lp0.

Wiki: printer-usb-transport marked HARDWARE-VERIFIED (lab 2026-07-07:
full slip + feed + cut over USB — parity with TCP).

Claude-Session: https://claude.ai/code/session_01Xcm6ikLgGoCxxHrxtjkk5V

wiki/log.md

@@ -2496,3 +2496,12 @@ close. writeAllUsb now holds back the FINAL byte as its own write — usblp's on
 acceptance a completion certificate for everything before it — then drains 300ms for that single
 packet before close. Tests updated (+ final-byte-alone assertion). [[printer-usb-transport]] has
 the full kernel-level account.
+
+## [2026-07-07] update | USB printing HARDWARE-VERIFIED; wizard lists real /dev/usb devices
+
+Lab retest after the close-cancel fix: full slip + feed + CUT over USB — parity with TCP; the
+transport is done. Follow-up UX (operator had to `ls /dev/usb` to find lp1 on park-buzi): new
+GET /api/setup/usb-printers enumerates /dev/usb/lpN + sysfs ieee1284_id make/model; the wizard's
+devicePath is now a select of PRESENT printers (fresh form preselects the first; a saved-but-
+absent path stays selectable, flagged; none found → free-text + hint). Transport option label no
+longer hardcodes lp0. Details on [[printer-usb-transport]].