Add {fmt} and <format> alignment support

[mborland]

No description provided.

[cppalliance-bot]

An automated preview of the documentation is available at https://301.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.

2026-01-28 19:56:31 UTC

[codecov]

Codecov Report

❌ Patch coverage is 95.65217% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 98.91%. Comparing base (9c2ab0e) to head (c069c31).
⚠️ Report is 5 commits behind head on develop.

Files with missing lines	Patch %	Lines
include/boost/int128/format.hpp	93.10%	4 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #301      +/-   ##
===========================================
- Coverage    98.97%   98.91%   -0.06%     
===========================================
  Files           59       59              
  Lines         5157     5245      +88     
  Branches      1569     1609      +40     
===========================================
+ Hits          5104     5188      +84     
- Misses          26       30       +4     
  Partials        27       27              

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