[ktz03]

Poly centers a floating-point scores array in place. This changes caller-owned arrays, including the parent of a sliced view, and raises ValueError: output array is read-only for read-only scores. The latter also prevents constructing a design matrix with C(a, Poly(scores)).

Center the scores into a new array before constructing the polynomial basis. Preserve the existing contrast values and column suffixes, and add direct contrast and formula/prediction regressions covering writable, read-only and shared-view inputs, with list and integer-array controls.

Validation on Windows, Python 3.13.15, NumPy 2.5.4, SciPy 1.18.1 and pandas 3.0.6:

• The same 14 new tests produce 10 failures and 4 passing controls on the unmodified implementation, then all pass with the fix.
• The complete suite passes 161 tests with 1 existing skip, both normally and in the official PATSY_AVOID_OPTIONAL_DEPENDENCIES=1 mode. pandas and SciPy remain installed in that compatibility-mode run.
• The official API-reference check, Ruff 0.16.10 formatting check for both changed files and git diff --check pass.

No R runtime comparison, other platform or complete upstream CI matrix was run locally.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.45%. Comparing base (331879f) to head (3c5ba5d).
⚠️ Report is 83 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #275      +/-   ##
==========================================
+ Coverage   97.60%   98.45%   +0.84%     
==========================================
  Files          30       31       +1     
  Lines        3096     3110      +14     
  Branches      591      676      +85     
==========================================
+ Hits         3022     3062      +40     
+ Misses         39       27      -12     
+ Partials       35       21      -14     

Flag	Coverage Δ
unittests	98.07% <100.00%> (+0.46%)	⬆️

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[bashtage]

Thanks.