fix: improve pep440-master git ref handling

[kiyoon]

Summary

• normalize pep440-master commit hashes to 7 hex characters excluding the g prefix
• let the master-connection lookup recognize origin/master and origin/main via git branch -a --contains
• add a just format recipe and apply matching YAML formatting in GitHub workflows

Verification

• ran python3 -m compileall src/version_pioneer/versionscript.py
• verified get_version_dict_wo_exec(..., style='pep440-master') now emits fixed-width 7-char hashes
• verified the connection lookup works in a clone shape with no local master branch but with remotes/origin/master

[codecov]

Codecov Report

❌ Patch coverage is 9.09091% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 47.90%. Comparing base (4e81205) to head (53fe31a).
⚠️ Report is 3 commits behind head on master.

Files with missing lines	Patch %	Lines
src/version_pioneer/versionscript.py	9.09%	10 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master       #8      +/-   ##
==========================================
- Coverage   54.28%   47.90%   -6.39%     
==========================================
  Files           9        9              
  Lines         875      883       +8     
==========================================
- Hits          475      423      -52     
- Misses        400      460      +60     

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