refactor swapaxes to object

[henrydingliu]

Summary of Changes

Changing all instance of xp.swapaxes(arr,...) to arr.swapaxes(...) , in order to reduce reliance on xp

Related GitHub Issue(s)

refers #1031

Additional Context for Reviewers

• I passed tests locally for both code (uv run pytest) and documentation changes (uv run jb build docs --builder=custom --custom-builder=doctest)

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Note

Low Risk
Mechanical, behavior-equivalent refactor with no algorithm or API changes; risk is limited to backend parity if a non-NumPy/CuPy array module lacked .swapaxes.

Overview
Replaces xp.swapaxes(arr, …) with arr.swapaxes(…) across bootstrap ODP resampling, Clark/Munich development, standard Development regression params, Cape Cod apriori weighting, and WeightedRegression std_err_fill, so axis swaps go through the array API instead of the backend module (issue #1031).

A test helper in test_development.py is updated the same way; the only other diff there is a trailing newline at EOF.

^{Reviewed by Cursor Bugbot for commit 1851900. Bugbot is set up for automated code reviews on this repo. Configure here.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.43%. Comparing base (921bfca) to head (1851900).
⚠️ Report is 17 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1084      +/-   ##
==========================================
+ Coverage   89.75%   90.43%   +0.68%     
==========================================
  Files          91       91              
  Lines        5408     5564     +156     
  Branches      696      752      +56     
==========================================
+ Hits         4854     5032     +178     
+ Misses        389      375      -14     
+ Partials      165      157       -8     

Flag	Coverage Δ
unittests	90.43% <100.00%> (+0.68%)	⬆️

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[github-actions]

Pyright Type Completeness

View the full pyright --verifytypes output for this commit

Project (full chainladder package, at this PR's head): 14.1% of exported symbols fully typed (175 / 1239)

	Known	Ambiguous	Unknown	Total
Project (head)	175	107	957	1239

Other symbols referenced but not exported by chainladder: 13

	Known	Ambiguous	Unknown	Total
Other (head)	3	1	9	13

Symbols without documentation:

• Functions without docstring: 314
• Functions without default param: 0
• Classes without docstring: 10

Patch (exported symbols added or changed by this PR): no exported symbol type-completeness changes detected.