test(build): Zuse's minted pair as a stick -- the acceptance boots and the sessions use it

mkdiskimage.sh --starship-from IDENT ART lays a minted pair out as a StarshipOS stick: an identity
partition holding IDENT's bytes and an Artemis partition holding ART's, each exactly its file's
size (Artemis's signature and fence are placed from the volume's size). kernel/Makefile: a
zusestick target, made fresh for every boot, is ZUSEDISK's default (ZUSE_PAIR names the pair);
STICK_PAIR puts the pair in the PC stick. qemu_session.py's Zuse drive is the pair as a stick.
check_images.sh checks both forms byte for byte against the pair (60 PASS).

On today's kernel all 23 sessions pass on the Zuse stick, and acceptance: amd64, aarch64,
riscv64 to [zuse@Hera] ok>, POST 538/538, dict_hash 0xfec8c47cfc6f437f; v4 suite and test-32
0 failures. The plan gains Task 5, screen=boot (ruled 2026-10-28).

Plan: docs/v4.0.0/plans/2026-10-27-stick-4-one-disk.md, Task 1 (R1 as recommended).

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

scripts/mkdiskimage.sh

@@ -23,6 +23,13 @@
 # StarshipOS Artemis partition to the last whole MiB before the backup GPT,
 # formatted and signed by TOOL (tools/mkartemis.c). Every partition starts and
 # ends on a whole MiB, so on 1 KiB blocks, as the kernel's GPT reader needs.
+#
+# Zuse's minted pair as a stick (docs/v4.0.0/plans/2026-10-27-stick-4-one-disk.md, Task 1):
+#   --starship-from IDENT_IMG ART_IMG --esp-mib E      (no --size-mib, no --mkartemis)
+# the same layout, but the identity partition is exactly IDENT_IMG's size and holds its bytes,
+# and the Artemis partition is exactly ART_IMG's size and holds its bytes (Artemis's signature
+# and fence are placed from the volume's size, so it cannot grow). Each must be a whole MiB.
+# The image is 1 + E + |IDENT_IMG| + |ART_IMG| + 1 MiB.
 # --table mbr  -> partition type 0x0c FAT32 (LBA)  (Raspberry Pi firmware)
 # DEST is an absolute path inside the FAT filesystem; parent directories are
 # created as needed.
@@ -31,7 +38,7 @@
 # root, no loop devices.
 set -euo pipefail
 
-OUT="" TABLE="" SIZE_MIB="" LABEL="" IDENT_MIB="" MKARTEMIS="" ESP_MIB=""
+OUT="" TABLE="" SIZE_MIB="" LABEL="" IDENT_MIB="" MKARTEMIS="" ESP_MIB="" FROM_IDENT="" FROM_ART=""
 while [ $# -gt 0 ]; do
     case "$1" in
         --out)      OUT="$2"; shift 2 ;;
@@ -41,12 +48,25 @@ while [ $# -gt 0 ]; do
         --starship) IDENT_MIB="$2"; shift 2 ;;
         --mkartemis) MKARTEMIS="$2"; shift 2 ;;
         --esp-mib)  ESP_MIB="$2"; shift 2 ;;
+        --starship-from) FROM_IDENT="$2"; FROM_ART="$3"; shift 3 ;;
         --) shift; break ;;
         -*) echo "mkdiskimage.sh: unknown option $1" >&2; exit 2 ;;
         *) break ;;
     esac
 done
 
+if [ -n "$FROM_IDENT" ]; then
+    [ "$TABLE" = gpt ] && [ -n "$ESP_MIB" ] && [ -z "$SIZE_MIB" ] && [ -z "$MKARTEMIS" ] || {
+        echo "mkdiskimage.sh: --starship-from needs --table gpt and --esp-mib, and no --size-mib or --mkartemis" >&2; exit 2; }
+    for f in "$FROM_IDENT" "$FROM_ART"; do
+        [ -f "$f" ] || { echo "mkdiskimage.sh: missing input $f" >&2; exit 1; }
+        [ $(( $(stat -c %s "$f") % 1048576 )) -eq 0 ] || { echo "mkdiskimage.sh: $f is not a whole MiB" >&2; exit 2; }
+    done
+    IDENT_MIB=$(( $(stat -c %s "$FROM_IDENT") / 1048576 ))
+    FROM_ART_MIB=$(( $(stat -c %s "$FROM_ART") / 1048576 ))
+    SIZE_MIB=$(( 1 + ESP_MIB + IDENT_MIB + FROM_ART_MIB + 1 ))
+    MKARTEMIS=-
+fi
 [ -n "$OUT" ] && [ -n "$TABLE" ] && [ -n "$SIZE_MIB" ] && [ -n "$LABEL" ] || {
     echo "mkdiskimage.sh: --out, --table, --size-mib and --label are required" >&2; exit 2; }
 if [ -n "$IDENT_MIB" ]; then
@@ -79,6 +99,7 @@ if [ -n "$IDENT_MIB" ]; then
     IDENT_SECTORS=$(( IDENT_MIB * 2048 ))
     ART_START=$(( IDENT_START + IDENT_SECTORS ))
     ART_SECTORS=$(( (LAST + 1 - ART_START) / 2048 * 2048 ))
+    [ -z "$FROM_ART" ] || ART_SECTORS=$(( FROM_ART_MIB * 2048 ))
     [ "$ART_SECTORS" -gt 0 ] || { echo "mkdiskimage.sh: no room for Artemis in ${SIZE_MIB} MiB" >&2; exit 2; }
 fi
 
@@ -94,8 +115,13 @@ if [ -n "$IDENT_MIB" ]; then
         printf 'start=%d, size=%d, type=%s, name="StarshipOS identity"\n' "$IDENT_START" "$IDENT_SECTORS" "$IDENT_TYPE"
         printf 'start=%d, size=%d, type=%s, name="StarshipOS Artemis"\n' "$ART_START" "$ART_SECTORS" "$ART_TYPE"
     } | sfdisk --quiet "$OUT"
-    "$MKARTEMIS" --format "$OUT" --first-lba "$ART_START" --sectors "$ART_SECTORS" >/dev/null || {
-        echo "mkdiskimage.sh: formatting Artemis failed" >&2; rm -f "$OUT"; exit 1; }
+    if [ -n "$FROM_IDENT" ]; then
+        dd if="$FROM_IDENT" of="$OUT" bs=1M seek=$(( IDENT_START / 2048 )) conv=notrunc,sparse status=none
+        dd if="$FROM_ART" of="$OUT" bs=1M seek=$(( ART_START / 2048 )) conv=notrunc,sparse status=none
+    else
+        "$MKARTEMIS" --format "$OUT" --first-lba "$ART_START" --sectors "$ART_SECTORS" >/dev/null || {
+            echo "mkdiskimage.sh: formatting Artemis failed" >&2; rm -f "$OUT"; exit 1; }
+    fi
     if [ "$ESP_MIB" = 0 ]; then
         echo "  IMAGE   $OUT (gpt, ${SIZE_MIB} MiB: StarshipOS identity ${IDENT_MIB} MiB, Artemis $(( ART_SECTORS / 2048 )) MiB)"
         exit 0