Merge to master for 3.1.0

[mborland]

Significant documentation improvements, and bug fixes for formatting support

[cppalliance-bot]

An automated preview of the documentation is available at https://417.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.

2026-07-08 14:19:17 UTC

[codecov]

Codecov Report

❌ Patch coverage is 96.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 96.21%. Comparing base (aac19ec) to head (c9fb1eb).
⚠️ Report is 37 commits behind head on master.

Files with missing lines	Patch %	Lines
include/boost/int128/format.hpp	93.33%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #417      +/-   ##
==========================================
+ Coverage   96.19%   96.21%   +0.02%     
==========================================
  Files          79       79              
  Lines        7068     7063       -5     
  Branches     2450     2450              
==========================================
- Hits         6799     6796       -3     
+ Misses         34       31       -3     
- Partials      235      236       +1     

☔ View full report in Codecov by Harness.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.