Skip molecules with zero count in Packmol wrapper

[mattwthompson]

Description

Resolves #1267, independently of #1268

Checklist

• Add tests
• Lint
• Update docstrings

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.86%. Comparing base (4ce92a9) to head (6deb6f8).
⚠️ Report is 56 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1272   +/-   ##
=======================================
  Coverage   93.86%   93.86%           
=======================================
  Files          72       72           
  Lines        6240     6242    +2     
=======================================
+ Hits         5857     5859    +2     
  Misses        383      383           

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[j-wags]

Some nonblocking docs and test recommendations, but otherwise this is good to go! You might also consider explicitly adding Closes #1267 to the body text so the issue is auto-closed.

[j-wags]

(not blocking) may be a hair more robust if the molecule with zero copies is not a duplicate of another mol in the list

[j-wags]

(not blocking) Also could be improved by putting it in the middle of the list, in case some off-by-one issue is being masked by it being at the end

[mattwthompson]

Thanks for the review!

I always though all closing keywords were the same?

I'll leave as-is to see what happens but check on it after