fix(fmt/smi): treat non-ring implicit aromatic bond as single bond

[jnooree]

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Linked Issues

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• Fixes [BUG] most smiles omit non-ring single bonds between aromatic atoms #287.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.84%. Comparing base (48caa15) to head (ba7ebe1).
Report is 3 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #288      +/-   ##
==========================================
+ Coverage   90.79%   90.84%   +0.04%     
==========================================
  Files          37       37              
  Lines        8669     8682      +13     
==========================================
+ Hits         7871     7887      +16     
+ Misses        798      795       -3     

Files	Coverage Δ
src/fmt/smiles.cpp	95.37% <100.00%> (+0.13%)	⬆️

... and 1 file with indirect coverage changes