Fix #109: Add LCS to MaximumIndependentSet reduction

[zazabap]

Summary

• Adds implementation plan for LongestCommonSubsequence model and LCS → MaximumIndependentSet reduction rule
• Plan covers: LCS model implementation, match-graph reduction (Apostolico & Guerra, 1987), unit tests, example program, paper documentation, and export regeneration

Closes #109

[codecov]

Codecov Report

❌ Patch coverage is 98.11321% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 96.89%. Comparing base (a88812b) to head (7eac728).

Files with missing lines	Patch %	Lines
.../longestcommonsubsequence_maximumindependentset.rs	95.89%	3 Missing ⚠️
.../longestcommonsubsequence_maximumindependentset.rs	96.25%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #173      +/-   ##
==========================================
+ Coverage   96.88%   96.89%   +0.01%     
==========================================
  Files         200      204       +4     
  Lines       27537    27855     +318     
==========================================
+ Hits        26680    26991     +311     
- Misses        857      864       +7     

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