wip(build): acceptance boots a fresh data stick -- every run is a first boot (#92, Task 3) [skip ci]

Not yet accepted (plan 2026-10-29-stick-5, Task 3).
- kernel/Makefile: a v4 `qemu` boot attaches a fresh data stick
  (DATASTICK=1) and nothing else; ARTDISK/ZUSEDISK keep the minted pair only
  for system=v3 (QEMU_V3_BOOT, from KERNEL_ARGS).
- qemu_session.py: the Makefile's defaults for every mode but those that ask
  for the pair by name (stick_artemis, two_sticks, artemis_unsigned,
  raw_ident, v3_keys) or for no drive; `zuse` now expects the genesis line.
- nightly.sh: accept stick-high runs stick_genesis (the stick as built).
- .claude/CLAUDE.md "The disks", the stick-high line; disk/README.md (the
  pair: tests and v3 only); STICK.md 11, increments 3 and 5 done.

Before the change: zuse on amd64 FAIL -- the pair's "identity confirmed",
no genesis line (logs/20261108-130732).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GE3SDvQn5EoxdGufk84zz2

kernel/Makefile

@@ -134,12 +134,17 @@ DOE_RUNS_DIR       := experiments/bare_metal/runs
 DOE_LATEST_DIR     := experiments/bare_metal/latest
 
 CAPSULES_DIR       ?= capsules
-# ARTDISK and ZUSEDISK default to the minted Zuse pair (disk/zuse-scratch/,
+# The disks a `qemu` boot attaches (plan 2026-10-29-stick-5, Task 3; STICK.md 9). A v4 boot -- every
+# boot but `system=v3` -- attaches a fresh data stick (DATASTICK, below) and nothing else: every
+# acceptance run is a first boot, the proxy Zuse minted on it, the prompt with nothing set up. A
+# `system=v3` boot (KERNEL_ARGS) keeps the defaults it has always had: the minted pair below.
+QEMU_V3_BOOT       := $(findstring system=v3,$(KERNEL_ARGS))
+# For system=v3: ARTDISK and ZUSEDISK default to the minted Zuse pair (disk/zuse-scratch/,
 # disk/README.md; Captain Bob, 2026-10-26, the identity gate's D4): with no
 # identity drive the system is headless, so a boot with the blank
 # disk/artemis.img and thumbdrives/zuse-thumb-ident.img never reaches a
 # prompt. The two are a pair: Zuse's genesis marker is on that Artemis disk.
-ARTDISK            ?= disk/zuse-scratch/artemis.img
+ARTDISK            ?= $(if $(QEMU_V3_BOOT),disk/zuse-scratch/artemis.img)
 # ARTDISK= (empty) attaches no virtio disk. Since 2026-10-28 the v4 boot takes Artemis only from the
 # stick (docs/v4.0.0/plans/2026-10-27-stick-4-one-disk.md, Task 4); ARTDISK stays for system=v3.
 # Precomputed for the same comma reason as ZUSEDISK_QEMU_ARGS below.
@@ -190,7 +195,7 @@ XHCI_ARGS_SLOT4    := $(if $(strip $(XHCI_QEMU_ARGS)),$(XHCI_QEMU_ARGS),$(XHCI_D
 # fresh for every boot), identity and Artemis partitions on one disk, as STICK.md 4 has them.
 ZUSE_PAIR          ?= disk/zuse-scratch
 ZUSESTICK_IMG       = $(BUILD_DIR)/zusestick.img
-ZUSEDISK           ?= $(ZUSESTICK_IMG)
+ZUSEDISK           ?= $(if $(QEMU_V3_BOOT),$(ZUSESTICK_IMG))
 ZUSESTICK_DEP       = $(if $(filter $(ZUSESTICK_IMG),$(ZUSEDISK)),zusestick)
 # Precomputed (not inlined as $(if ...,...)) because the drive/device specs
 # below are comma-heavy and GNU make's $(if) function splits its own
@@ -203,12 +208,12 @@ ZUSEDISK_QEMU_ARGS := -drive if=none,id=zusedrv,file=$(ZUSEDISK),format=raw -dev
 else
 ZUSEDISK_QEMU_ARGS :=
 endif
-# DATASTICK -- set to 1 to attach the data stick (`make ... datastick`: StarshipOS identity
-# and Artemis partitions, no ESP, made fresh before the boot) over USB on port 2, beside the
-# disks above (docs/v4.0.0/STICK.md 9). Off by default until the first boot of a fresh data
-# stick can mint Zuse (increment 5, which turns it on and retires ARTDISK/ZUSEDISK;
-# docs/v4.0.0/plans/2026-10-27-stick-3-images.md, ruled 2026-10-27).
-DATASTICK          ?=
+# DATASTICK -- 1 attaches the data stick (`make ... datastick`: StarshipOS identity and Artemis
+# partitions, no ESP, made fresh before the boot) over USB on port 2 (docs/v4.0.0/STICK.md 9).
+# On by default for a v4 boot since a fresh data stick's first boot mints Zuse (plan
+# 2026-10-29-stick-5, Task 3, as stick-3's ruling of 2026-10-27 set out); off for system=v3.
+# DATASTICK= boots v4 with no drive at all (headless).
+DATASTICK          ?= $(if $(QEMU_V3_BOOT),,1)
 ifneq ($(strip $(DATASTICK)),)
 DATASTICK_QEMU_ARGS = -drive if=none,id=datadrv,file=$(DATASTICK_IMG),format=raw -device usb-storage,bus=xhci0.0,port=2,drive=datadrv
 DATASTICK_DEP      := datastick