fix: unwanted promotion in copysign

[avik-pal]

No description provided.

[codecov]

Codecov Report

❌ Patch coverage is 33.33333% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 42.57%. Comparing base (e201029) to head (d7cf86d).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/TracedRNumber.jl	33.33%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1590      +/-   ##
==========================================
+ Coverage   42.06%   42.57%   +0.51%     
==========================================
  Files         123      123              
  Lines       21617    21801     +184     
==========================================
+ Hits         9093     9282     +189     
+ Misses      12524    12519       -5     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

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