Constant DIAG_CD_ERROR 

pub const DIAG_CD_ERROR: u8 = 0x05; // 5u8

Moved to psx_io::cd::reader. Kept at this path for one stage so psx_pack::cd::SectorReader still resolves; a re-export cannot carry a deprecation. SectorReader::diagnostics cause byte: the drive raised INT5; the snapshot carries the error response’s status and error-code bytes.