Parse the HEADER section of a STEP/IFC buffer into IfcSourceHeader.
Returns undefined when no recognisable header records are present (e.g.
non-STEP input). Cheap: only the first MAX_HEADER_BYTES are decoded,
truncated at the first ENDSEC so the DATA section is never scanned.
Parse the HEADER section of a STEP/IFC buffer into IfcSourceHeader. Returns
undefinedwhen no recognisable header records are present (e.g. non-STEP input). Cheap: only the first MAX_HEADER_BYTES are decoded, truncated at the firstENDSECso the DATA section is never scanned.