Legacy BOOTIMG package contract

Y2B-230 packages only the validated payload. Offline inspection of the owner-proven FM boot.img confirmed ANDROID!, 2048-byte page size, header fields kernel_addr=0x10008000, ramdisk_addr=0x11000000, second_addr=0x10f00000, tags_addr=0x10000100, zero second/DT sizes, empty header cmdline, and SHA-1 over each wrapped kernel/ramdisk section followed by its little-endian size, then zero second size. These are legacy header fields; FM LK's actual load/entry addresses remain D08's 0x80008000 and 0x84000000.

Each MTK wrapper is 512 bytes: little-endian magic 0x58881688, inner byte length, 32-byte NUL-padded KERNEL or ROOTFS name, then 472 bytes of 0xff. New header name is deterministic Y2Linux-M1; trailing ID bytes and unused header bytes are zero. Neither the old Android SHA-1 ID nor SHA-256 manifest constitutes an image signature or proves installed LK acceptance.

Output is Android header page + page-padded wrapped kernel + page-padded wrapped initramfs + two explicit zero pages. This covers the entire additional LK read traced in Y2E-125/D08 instead of relying on stale partition tail contents. The resulting file must equal 2048 + align_up(K,2048) + align_up(W,2048) + 4096 and be no larger than the 16 MiB BOOTIMG partition. All page padding is zero. The parser checks every field, payload byte, SHA-1 ID, wrapper and padding extent independently before output is written. No flasher or partition-access code exists in this build path.