D002 - The generation is a type with no default

Status: decided Date: 2026-09-26

Generation has no Default, and every builder takes the target generation explicitly. The container magic is a [u8; 4], not an integer.

Why: the two generations' containers differ only in the magic, so a wrong generation is structurally perfect and refused by a loader as "not a container". A default hides that choice. Held as an integer the magic looks right and serialises in the wrong byte order.

Rejected:

• A default generation: the caller never states the one thing that differs.
• The magic as a u32 constant: correct in source, reversed on disk.