nrf52Bootloader

The board-agnostic bootloader-driven erase image (OTAFIX tools/meshtastic_factory_erase.uf2): a single UF2 block the bootloader itself consumes when its INFO_UF2.TXT advertises Factory-Erase: UF2 family <id>. Absent from manifests that predate it, and ignored by bootloaders that do not advertise it — so it is only ever preferred over nrf52, never a replacement for it.