Significantly expand and improve examples of rounding mode manipulation

[mborland]

Closes: #1196

[cppalliance-bot]

An automated preview of the documentation is available at https://1246.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.

2025-11-14 13:40:25 UTC

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.1%. Comparing base (0abe29a) to head (a4809e0).
⚠️ Report is 10 commits behind head on develop.

Additional details and impacted files

@@            Coverage Diff            @@
##           develop   #1246     +/-   ##
=========================================
- Coverage     99.1%   99.1%   -0.0%     
=========================================
  Files          264     264             
  Lines        17251   17251             
  Branches      1931    1931             
=========================================
- Hits         17080   17079      -1     
- Misses         171     172      +1     

see 1 file with indirect coverage changes

---

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 0abe29a...a4809e0. Read the comment docs.

🚀 New features to boost your workflow:

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