Constant FORMAT 

pub const FORMAT: u32 = 2;

The bundle format version, stamped into every bundle and checked on load.

• 1 — postcard over a mirror of Core, with types erased.
• 2 — plus reads_freshness: whether the view observes §3.7’s freshness dimension. postcard is not self-describing, so a field added is a format changed; the alternative was a kernel deciding it by looking for a variable in the view’s body, which is a guess about the splitter’s output rather than a fact from it.