Add C++26 integer comparison functions

[mborland]

Closes: #443

[cppalliance-bot]

An automated preview of the documentation is available at https://460.int128.prtest3.cppalliance.org/libs/int128/doc/html/index.html

If more commits are pushed to the pull request, the docs will rebuild at the same URL.

2026-07-24 18:45:25 UTC

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.01%. Comparing base (3382905) to head (d0dd219).
⚠️ Report is 14 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #460      +/-   ##
===========================================
+ Coverage    95.99%   96.01%   +0.01%     
===========================================
  Files           83       87       +4     
  Lines         7323     7630     +307     
  Branches      2595     2774     +179     
===========================================
+ Hits          7030     7326     +296     
  Misses          54       54              
- Partials       239      250      +11     

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