feat(build): make write_stick DEVICE=/dev/sdX -- the PC stick onto a USB stick, checked and read back

scripts/write_stick.sh refuses a device that is not a whole, removable USB disk, that holds the
running system, that is smaller than the image, or that has a mounted partition (it prints the
udisksctl lines); shows the stick and asks for its name typed back; writes with conv=fsync,
flushes, reads the stick back and compares it with the image byte for byte; powers it off. On
Windows/macOS it points to balenaEtcher or Rufus. Captain Bob, 2026-10-28, after a terminal line
break dropped dd's bs=4M conv=fsync on the first SER5 stick.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Makefile

@@ -20,6 +20,9 @@
 #                                     (build/boards/<board>/*.spdx*) and a fresh
 #                                     source SBOM -- needs syft
 #   make boot_images                  every board that has a kernel port
+#   make write_stick DEVICE=/dev/sdX  write the PC stick image to a USB stick, checked
+#                                     first, read back and compared after
+#                                     (scripts/write_stick.sh; Linux, sudo)
 #   make docs [TARGET=<board>]        the book; a board adds its appendix
 #
 #   make clean                        all of build/ except build/cache/
@@ -59,7 +62,7 @@ BOARD_DIR := $(if $(TARGET),$(BOARD_DIR_$(TARGET)))
 SUBMAKE := $(MAKE) --no-print-directory
 
 .DEFAULT_GOAL := all
-.PHONY: all boot_image boot_images docs clean clean-docs kernel boards help help-hosted sbom sbom-board \
+.PHONY: all boot_image boot_images write_stick docs clean clean-docs kernel boards help help-hosted sbom sbom-board \
         qemu qemu-esp qemu-gdb
 
 # ARCH given on the command line and no TARGET: `clean` is the kernel's for that
@@ -222,6 +225,13 @@ boards:
 	@$(foreach b,$(BOARDS),printf '  %-9s %-8s %s\n' "$(b)" \
 	    "$(if $(call board_ready,$(b)),ready,no port)" "$(call board_field,$(b),BOARD_DESC)";)
 
+# write_stick -- the PC stick image (make boot_image TARGET=PC) onto a USB stick, safely:
+# scripts/write_stick.sh refuses anything but a whole, removable, unmounted USB disk big enough,
+# asks for the device to be typed back, writes, flushes, reads back and compares.
+write_stick:
+	@[ -n "$(DEVICE)" ] || { echo "Usage: make write_stick DEVICE=/dev/sdX   (lsblk lists the disks)"; exit 1; }
+	@bash scripts/write_stick.sh build/boards/pc/lithos-pc.img $(DEVICE)
+
 help:
 	@sed -n '/^# TARGET is/,/^# =====/p' Makefile | sed '$$d; s/^# \{0,1\}//'