Treat float 1.0 as a singular count

[gaoflow]

Summary

• treat numeric count values equal to 1, such as 1.0, as singular counts
• keep non-numeric string counts on the existing string-based path
• add regression coverage for get_count(1.0) and plural(..., 1.0)

Fixes #232

Verification

• python -m pytest tests/test_pwd.py -k "count or plural" -q
• python -m pytest -q
• python -m compileall inflect tests
• python -m ruff format --check inflect/init.py tests/test_pwd.py
• git diff --check upstream/main...HEAD

Note: python -m ruff check inflect/init.py tests/test_pwd.py still reports pre-existing UP006/UP007/UP035 typing modernization diagnostics across inflect/init.py that are unrelated to this change.