[Plastic-time]

The Simplified Chinese catalog has empty translations for zero, milliseconds, microseconds, and the conjunction used by precisedelta(). With zh_CN active, this produces English output such as 1 millisecond and mixed output such as 1分 and 1秒.

Changes proposed in this pull request:

• Fill those four catalog entries, retaining the existing compact Chinese spacing.
• Add tests for singular/plural subsecond durations, zero, and combined durations.

All five regression cases fail with the original compiled catalog. After recompiling the catalogs with polib, the full suite passes on Python 3.12: 881 passed, 2 skipped. The skipped tests require GNU gettext command-line tools, which are unavailable locally; the new Chinese tests all run and pass. Ruff and Black pass for the changed test file.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.35%. Comparing base (418a6ae) to head (01545b9).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #472   +/-   ##
=======================================
  Coverage   97.35%   97.35%           
=======================================
  Files          12       12           
  Lines        1022     1022           
=======================================
  Hits          995      995           
  Misses         27       27           

Flag	Coverage Δ
macos-latest	97.26% <ø> (ø)
ubuntu-latest	95.00% <ø> (ø)
windows-latest	95.00% <ø> (ø)

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[hugovk]

Thanks, I resolved the conflict and dropped the tests, we don't really need them here.