pub const BUILTIN_REVISION: Revision;Expand description
A builtin’s nominal revision: 0, always. A builtin is not an
observation of anything – it ships with the binary and has no author
writing successive edits for didbot_policy::Revision to order, so
there is nothing for this value to compare against. It exists only
because didbot_policy::PolicyDeclaration always carries one, for
plan/policy.md’s “record which policy version admitted each write”.