Make bitwise operations for signed integers illegal, and provide rationale

[mborland]

Closes: #33

[cppalliance-bot]

An automated preview of the documentation is available at https://177.safe-numbers.prtest3.cppalliance.org/libs/safe_numbers/doc/html/index.html

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

2026-04-15 19:46:09 UTC

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.6%. Comparing base (fe937e4) to head (33aa429).
⚠️ Report is 6 commits behind head on develop.

Additional details and impacted files

@@           Coverage Diff           @@
##           develop    #177   +/-   ##
=======================================
  Coverage     97.6%   97.6%           
=======================================
  Files          166     166           
  Lines        12670   12670           
  Branches      4660    4660           
=======================================
  Hits         12356   12356           
  Misses         247     247           
  Partials        67      67           

Files with missing lines	Coverage Δ
...boost/safe_numbers/detail/signed_integer_basis.hpp	84.1% <ø> (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 fe937e4...33aa429. Read the comment docs.

🚀 New features to boost your workflow:

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