Summary

• convert decimal and hexadecimal numeric character references independently
• keep invalid numeric references unchanged so later slug cleanup can handle them
• add regression coverage for mixed valid and invalid numeric references

Why

The previous implementation wrapped the whole regex substitution in one try block. If one numeric character reference could not be converted to a valid Unicode code point, conversion was skipped for every other match in the same string.

For example, Ž � produced 381-9999999999, even though the first reference is valid and should become z.

Checks

• python -m pytest -q -> 84 passed
• python -m mypy -> Success: no issues found in 5 source files
• python -m pycodestyle --ignore=E128,E261,E225,E501,W605 slugify test.py setup.py
• git diff --check