[MRG] Fix UCOOT partial init_duals crash, replace prints with errors/warnings, docstring fixes

[agramfort]

Types of changes

• Bug fix
• Documentation fixes
• Maintenance (pre-commit config, lint)

Motivation and context / Related issue

A small set of fixes from a review of the package. It contains no API redesign.

Bug fix

• ot.gromov.fused_unbalanced_across_spaces_divergence: the loop over [duals_samp, duals_feat] always unpacked duals_feat. As a result, init_duals=(duals_samp, None) crashed with a TypeError, and duals_samp was never used for backend detection, although the code further down explicitly supports partial duals.

Raise or warn instead of print

• ot.datasets.make_data_classif now raises ValueError on an unknown dataset (it used to print and return dummy arrays).
• ot.stochastic.solve_semi_dual_entropic now raises ValueError on an unknown method (it used to print and return None).
• ot.mapping.nearest_brenier_potential_* now raise ImportError when CVXPY is missing (they used to print and return None).
• ot.gaussian.bures_barycenter_fixpoint, ot.regpath and the entropic partial Wasserstein solver now emit UserWarning instead of printing.

Docs

• Fixed docstring parameters that did not match the signature:
  • epsilon → reg, a stale assume_inner_convergence entry and the wrong grad default in solve_gromov_batch
  • numItermax → numIterMax in empirical_sinkhorn*
  • log → use_log in GW dictionary learning
  • other wrong or stale names: d_instrinsic, weights/tplt_weights, K_1/K_2, v/beta and list_p2
  • removed entries for parameters that no longer exist
  • removed duplicated entries
• Fixed b being described as "source domain" in ot.solve/ot.solve_sample.
• Fixed typos, and a broken .hmtl link in the README.

Maintenance

• .pre-commit-config.yaml: the ruff hook for docs/examples/tests used the pattern ^examples/^test/ (missing |), so it never matched, and the ruff-format pattern ended in |, which matches every file. The second commit fixes the 18 lint errors already present in test/ that the corrected hook now reports.

How has this been tested (if it applies)

• New regression tests: test_partial_init_duals (UCOOT), invalid method in solve_semi_dual_entropic, unknown dataset (test/test_datasets.py), the non-convergence warning in bures_barycenter_fixpoint, and the max-iteration warning in regularization_path.
• Ran locally: datasets, regpath, stochastic, gaussian, ucoot, mapping, partial, smooth, dr, da, quantized GW, solvers, sliced, ot, batch, backend, bspot, sgot, utils, lowrank, gromov dictionary and gnn. All pass.
• ruff check and ruff format --check (0.5.2, as pinned in pre-commit) pass on ot/ and test/.

PR checklist

• I have read the CONTRIBUTING document.
• The documentation is up-to-date with the changes I made (check build artifacts).
• All tests passed, and additional code has been covered with new tests.
• I have added the PR and Issue fix to the RELEASES.md file.

🤖 Generated with Claude Code

[codecov]

Codecov Report

❌ Patch coverage is 92.30769% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 97.04%. Comparing base (604c47f) to head (d12c547).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #888      +/-   ##
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+ Coverage   97.00%   97.04%   +0.04%     
==========================================
  Files         128      129       +1     
  Lines       26349    26385      +36     
==========================================
+ Hits        25559    25606      +47     
+ Misses        790      779      -11     

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