Remove unreachable OCR-skip fallback (raw_bare can't be all-digits
if strip_ro_prefix changed it via OCR fix). Add real test for the
checksum result==10→0 branch using CUI 14186770.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Covers strip_ro_prefix (OCR fixes), validate_cui (format),
validate_cui_checksum (Romanian algorithm with key 753217532),
and sanitize_cui (end-to-end with warnings). Verified against
12 real CUIs from production orders.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>