feat: enhance smart grouping dependency handling

[Arakiss]

Summary

• improve SmartGrouper by prioritizing test grouping, caching file reads, and extracting dependencies from import statements
• add targeted tests covering dependency detection and enriched grouping metadata
• publish the 1.7.0 release with updated version metadata and changelog entry

Testing

• pytest

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https://chatgpt.com/codex/tasks/task_e_68caf74c4cd0832aa8e6257fd2415ddf

[codecov-commenter]

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Codecov Report

❌ Patch coverage is 70.07299% with 41 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
commitloom/core/smart_grouping.py	70.07%	28 Missing and 13 partials ⚠️
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@@            Coverage Diff             @@
##             main       #6      +/-   ##
==========================================
- Coverage   70.81%   70.67%   -0.14%     
==========================================
  Files           9        9              
  Lines        1350     1463     +113     
  Branches      206      234      +28     
==========================================
+ Hits          956     1034      +78     
- Misses        335      359      +24     
- Partials       59       70      +11     

Files with missing lines	Coverage Δ
commitloom/core/smart_grouping.py	84.09% <70.07%> (-7.96%)	⬇️

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