Negative interest invariance check

[slundqui]

Adding invariance check to ensure no negative interest between subsequent calls of invariance checks.

[codecov]

Codecov Report

Attention: Patch coverage is 73.68421% with 5 lines in your changes missing coverage. Please review.

Project coverage is 82.30%. Comparing base (8a4d151) to head (a938873).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...c/agent0/hyperfuzz/system_fuzz/invariant_checks.py	73.68%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1680      +/-   ##
==========================================
+ Coverage   81.73%   82.30%   +0.57%     
==========================================
  Files          99       99              
  Lines        7565     7584      +19     
==========================================
+ Hits         6183     6242      +59     
+ Misses       1382     1342      -40     

Flag	Coverage Δ
unittests	82.30% <73.68%> (+0.57%)	⬆️

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