Fix false CMIP7 QC failures at closed-range boundaries

[rbeucher]

Summary

• make CMIP7 range checks use a scale-aware float tolerance for closed-interval comparisons
• avoid false failures when boundary values (for example 100%) round slightly outside limits in float32-derived outputs
• add a regression test for snc with near-boundary percent values

Testing

• pixi run -e dev python -m pytest tests/unit/test_cmip7_qc.py -k "tiny_negative_noise_at_zero_bound or float32_boundary_noise_for_percent_range or tas_fails_for_picontrol_range" -q

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.7%. Comparing base (24d23cc) to head (fbda862).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #495   +/-   ##
=====================================
  Coverage   78.7%   78.7%           
=====================================
  Files         33      33           
  Lines       6548    6558   +10     
  Branches    1239    1242    +3     
=====================================
+ Hits        5153    5163   +10     
  Misses      1127    1127           
  Partials     268     268           

Flag	Coverage Δ
unit	78.7% <100.0%> (+<0.1%)	⬆️

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