the block's current version (selects the point encoding for lines)
the unread tail of the block, preserved for round-tripping
the deleted item's envelope (no value)
the block's minimum reader version
the parent group's crdt id
the header byte between the block length and the versions
Zero in every well-formed file seen, but preserved rather than assumed.
the block-type discriminant
the
0x08scene tombstone item block — a deleted-item marker