pub const ROLE_MODE_ITEM: &'static str;Expand description
The modeline role a mode tags content with when it
contributes a segment to the modeline (e.g. diff-mode’s +N ~M
stats) (DX.4, BC.6). Lives in lattice-mode (not host) because it is the role
modes reach for — ModelineRole::new(ROLE_MODE_ITEM) — so it belongs
with the mode-contribution substrate, letting lattice-diff reach it
without the host. The host’s own element roles (modeline.path,
modeline.position, modeline.lang, modeline.mode) stay host-side;
the host re-exports this one so renderer style maps + crate::modeline
call sites are unchanged.