Update numeric literals and documentation

[mborland]

Closes: #391

[cppalliance-bot]

An automated preview of the documentation is available at https://395.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.

2026-05-11 19:41:43 UTC

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.99%. Comparing base (cf2f0d4) to head (ccdf818).
⚠️ Report is 6 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff            @@
##           develop     #395   +/-   ##
========================================
  Coverage    95.99%   95.99%           
========================================
  Files           69       69           
  Lines         5938     5948   +10     
  Branches      1969     1972    +3     
========================================
+ Hits          5700     5710   +10     
  Misses          34       34           
  Partials       204      204           

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