test(stick): Artemis grows to fill the stick -- the tests, seen to fail (#92, Task 2) [skip ci]

Plan 2026-10-29-stick-5, Task 2, steps 1-2:
- qemu_session.py: --stick-gib N (the session's copy of the stick extended,
  sparse); modes stick_grow (16 GiB: grown, over 12000000 user blocks, the
  prompt, the first boot's time; the second boot of the same copy not grown
  again; sfdisk --verify clean) and stick_small (4 GiB: under 8 GB, not grown,
  said so).
- kernel/Makefile: STICK_GIB and STICK_FRESH on qemu-stick, for those.
- check_images.sh: the PC stick's and data stick's Artemis BAM sized for the
  256 GiB cap (6144 devblocks).

Before the change: stick_grow FAIL (no growth line, 1137649 user blocks,
sfdisk: the backup GPT not at the end); stick_small FAIL (no line);
check_images.sh FAIL on the two BAM checks only.

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

kernel/Makefile

@@ -1314,6 +1314,12 @@ else ifeq ($(ARCH),riscv64)
 STICK_PC_IMG       := build/boards/pc/lithos-pc.img
 STICK_MACHINE      ?= q35
 STICK_MEM          ?= 1024
+# STICK_GIB=N -- the copy booted is extended, sparse, to N GiB: a stick larger than the image
+# written to it (docs/v4.0.0/STICK.md 5a). STICK_FRESH=0 -- boot the copy the last boot left,
+# not a fresh one: a stick's second boot (plan 2026-10-29-stick-5, Task 2).
+STICK_GIB          ?=
+STICK_FRESH        ?= 1
+STICK_RUN_IMG       = $(BUILD_DIR)/stick-run.img
 .PHONY: qemu-stick qemu-stick-high
 qemu-stick-high:
 	@$(MAKE) -f kernel/Makefile ARCH=$(ARCH) STICK_MACHINE=pc STICK_MEM=3G qemu-stick
@@ -1322,7 +1328,10 @@ ifneq ($(ARCH),amd64)
 	@echo "qemu-stick: the stick is the PC's -- ARCH=amd64 (ARM and RISC-V sticks are later, STICK.md 10)"; exit 1
 else
 	@$(MAKE) -f kernel/Makefile ARCH=amd64 BOARD=pc boot_image
-	@cp --sparse=always $(STICK_PC_IMG) $(BUILD_DIR)/stick-run.img
+	@if [ "$(STICK_FRESH)" = 1 ] || [ ! -f $(STICK_RUN_IMG) ]; then \
+	    cp --sparse=always $(STICK_PC_IMG) $(STICK_RUN_IMG); \
+	    $(if $(STICK_GIB),truncate -s $(STICK_GIB)G $(STICK_RUN_IMG);) \
+	fi
 	@if [ ! -f $(OVMF_CODE) ];    then echo "Error: $(OVMF_CODE) not found";    exit 1; fi
 	@if [ ! -f $(OVMF_VARS_RO) ]; then echo "Error: $(OVMF_VARS_RO) not found"; exit 1; fi
 	@cp $(OVMF_VARS_RO) $(BUILD_DIR)/OVMF_VARS-stick.fd
@@ -1347,7 +1356,7 @@ else
 		-drive if=pflash,format=raw,readonly=on,file=$(OVMF_CODE) \
 		-drive if=pflash,format=raw,file=$(BUILD_DIR)/OVMF_VARS-stick.fd \
 		$(XHCI_ARGS_ROOT) \
-		-drive if=none,id=stickdrv,file=$(BUILD_DIR)/stick-run.img,format=raw \
+		-drive if=none,id=stickdrv,file=$(STICK_RUN_IMG),format=raw \
 		-device usb-storage,bus=xhci0.0,port=1,drive=stickdrv,bootindex=0 \
 		-chardev socket,id=cserial,path=$$SERIAL_SOCK,server=on,wait=off,logfile=$$LOG \
 		-serial chardev:cserial \