refactor: improve commit combo error handling and message clarity

[linw1995]

• Apply -E flag to bash for better error trap handling
• Add pre-commit failure message handler with automatic fix guidance
• Simplify git commit message prompt for more focused AI responses
• Use consistent heredoc format (<<EOF instead of <<-EOF)
• Improve error handling flow with ERR trap setup and cleanup

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 58.47%. Comparing base (f095ddf) to head (c66418d).
⚠️ Report is 6 commits behind head on dev.

Additional details and impacted files

@@            Coverage Diff             @@
##              dev      #85      +/-   ##
==========================================
- Coverage   59.37%   58.47%   -0.90%     
==========================================
  Files          77       81       +4     
  Lines       15921    18296    +2375     
==========================================
+ Hits         9453    10699    +1246     
- Misses       6468     7597    +1129     

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