is_member() (fail-closed) and add() (idempotent, chains new devblocks
onto the tail as needed) over the item-17 eligibility-list devblock
chain, mirroring capsule_zuse_boot.c's magic/version/CRC-64 validation
convention. No callers yet.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QgooKd5hJNtTYqB6CyK5f9
