Fix 2x parsing problems with literals (prefix and oversize value)

[mborland]

Closes: #437
Closes: #438

[cppalliance-bot]

An automated preview of the documentation is available at https://445.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.

2026-07-23 19:42:06 UTC

[codecov]

Codecov Report

❌ Patch coverage is 88.15789% with 9 lines in your changes missing coverage. Please review.
✅ Project coverage is 96.18%. Comparing base (f3aecea) to head (03c1e3d).
⚠️ Report is 23 commits behind head on develop.

Files with missing lines	Patch %	Lines
include/boost/int128/detail/mini_from_chars.hpp	78.04%	9 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #445      +/-   ##
===========================================
- Coverage    96.28%   96.18%   -0.10%     
===========================================
  Files           83       83              
  Lines         7268     7319      +51     
  Branches      2560     2593      +33     
===========================================
+ Hits          6998     7040      +42     
- Misses          31       40       +9     
  Partials       239      239              

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