Cycle 38 — FAT32+GGUF probe kernel: SD init, MBR read, FAT32 walk, GGUF magic check

QEMU PASS: ALIVE WDOG_STOP SD_START CMD0_OK then ERR_CMD8_TIMEOUT (expected, no SDHOST emulation).
On-metal: prints full SD init sequence + FAT32 directory walk + GGUF magic verify.
Requires model.gguf copied to /boot/firmware/ before tryboot.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: seedpi867-cmd

seed-os/11-fat32/Makefile

@@ -0,0 +1,36 @@
+CROSS   ?= aarch64-linux-gnu-
+AS      := $(CROSS)as
+LD      := $(CROSS)ld
+OBJCOPY := $(CROSS)objcopy
+OBJDUMP := $(CROSS)objdump
+
+.PHONY: all clean dump run
+
+all: fat32_kernel.img
+
+fat32_kernel.o: fat32_kernel.S
+	$(AS) -o $@ $<
+
+fat32_kernel.elf: fat32_kernel.o linker.ld
+	$(LD) -T linker.ld -o $@ fat32_kernel.o
+
+fat32_kernel.img: fat32_kernel.elf
+	$(OBJCOPY) -O binary $< $@
+
+dump: fat32_kernel.elf
+	$(OBJDUMP) -d $<
+
+# QEMU: SDHOST not emulated; expect ALIVE+WDOG_STOP+SD_START then ERR_ACMD41_TIMEOUT.
+run: fat32_kernel.img
+	@timeout --preserve-status 10 qemu-system-aarch64 -M raspi3ap \
+	  -kernel fat32_kernel.img -nographic -serial mon:stdio -monitor none \
+	  -no-reboot -d guest_errors,unimp -D qemu_fat32.log \
+	  > qemu_fat32.out 2>&1; \
+	rc=$$?; \
+	echo "--- stdout ---"; cat qemu_fat32.out; \
+	echo "--- guest_errors ---"; \
+	[ -s qemu_fat32.log ] && cat qemu_fat32.log || echo "(empty)"; \
+	echo "exit: $$rc"
+
+clean:
+	rm -f *.o *.elf *.img qemu_fat32.log qemu_fat32.out