Improve <cfenv> examples and docs

[mborland]

Closes: #1094
Closes: #1095

[cppalliance-bot]

An automated preview of the documentation is available at https://1101.decimal.prtest3.cppalliance.org/libs/decimal/doc/html/index.html

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

2025-10-10 08:00:24 UTC

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.4%. Comparing base (5446da0) to head (98082ef).
⚠️ Report is 18 commits behind head on develop.

Additional details and impacted files

@@            Coverage Diff            @@
##           develop   #1101     +/-   ##
=========================================
+ Coverage     99.4%   99.4%   +0.1%     
=========================================
  Files          245     246      +1     
  Lines        16770   16778      +8     
  Branches      1812    1812             
=========================================
+ Hits         16663   16671      +8     
  Misses         107     107             

Files with missing lines	Coverage Δ
include/boost/decimal/cfenv.hpp	100.0% <ø> (ø)
test/github_issue_1026.cpp	100.0% <ø> (ø)
test/github_issue_1094.cpp	100.0% <100.0%> (ø)

---

Continue to review full report in Codecov by Sentry.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 5446da0...98082ef. Read the comment docs.

🚀 New features to boost your workflow:

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