Raw device access. The single chokepoint through which bootsmith touches
/dev/rdiskN. Lives behind the Device trait from bootsmith-core.
Safety guards (the most important code in the project, after the boot records themselves):
- Refuse the boot disk.
- Refuse any disk flagged
internal: trueby DiskArbitration. - Refuse disks larger than 256 GiB without
--force. - Always operate on
/dev/rdiskN, never/dev/diskN.
Implementations are gated by cfg(target_os = ...). macOS is the only
target in v1; Linux is planned for v2.