Expand scientific notation floats in number_to_words

[gaoflow]

Summary

• expand numeric inputs rendered by Python in scientific notation before number_to_words() parses them
• add regression coverage for small and large floats that previously produced digit-grouped words

Closes #226

Tests

• PYTHONPATH=. uv run --python 3.11 --with '.[test]' pytest tests/test_numwords.py -q
• PYTHONPATH=. uv run --python 3.11 --with '.[test]' pytest -q
• PYTHONPATH=. uv run --python 3.11 --with '.[test,check]' ruff check --select I inflect/__init__.py tests/test_numwords.py
• PYTHONPATH=. uv run --python 3.13 --with '.[test]' pytest tests/test_numwords.py -q