perf: better integral

[34j]

Description of change

Pull-Request Checklist

• Code is up-to-date with the main branch
• This pull request follows the contributing guidelines.
• This pull request links relevant issues as Fixes #0000
• There are new or updated unit tests validating the change
• Documentation has been updated to reflect this change
• The new commits follow conventions outlined in the conventional commit spec, such as "fix(api): prevent racing of requests".

• If pre-commit.ci is failing, try pre-commit run -a for further information.
• If CI / test is failing, try uv run pytest for further information.

[codecov]

Codecov Report

❌ Patch coverage is 55.55556% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 64.07%. Comparing base (68de305) to head (bb986ed).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/ultrasphere/_integral.py	55.55%	2 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #59      +/-   ##
==========================================
- Coverage   64.38%   64.07%   -0.31%     
==========================================
  Files          12       12              
  Lines         598      604       +6     
  Branches       99      102       +3     
==========================================
+ Hits          385      387       +2     
- Misses        195      197       +2     
- Partials       18       20       +2     

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