pub const LAST: u8 = 0xFF /* 255u8 */;Expand description
Reserved axis sentinel = the trailing axis, resolved to rank-1 at eval
(§6.20-0002/-0003). Concrete axes are 0..MAX_RANK-1 (MAX_RANK=8), so 0xFF is
unambiguously last. DISTINCT from §6.19-0020’s 0xFFFE (u16 axis-set mask) — a
different field, different width.