feat: auto-exclude gitignore patterns

[twelvelabs]

This MR:

• Adds logic to auto exclude patterns from .gitignore when present.
• Adds a slight optimization when processing multiple path specs.

Closes #99

[codecov]

Codecov Report

Attention: 13 lines in your changes are missing coverage. Please review.

Comparison is base (22fd462) 91.96% compared to head (3b9d4bd) 92.17%.

Files	Patch %	Lines
internal/stylist/path_indexer.go	78.18%	8 Missing and 4 partials ⚠️
internal/stylist/pipeline.go	75.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #109      +/-   ##
==========================================
+ Coverage   91.96%   92.17%   +0.21%     
==========================================
  Files          18       19       +1     
  Lines        1742     1789      +47     
==========================================
+ Hits         1602     1649      +47     
  Misses         99       99              
  Partials       41       41              

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