more fixes

[henrydingliu]

Summary of Changes

Related GitHub Issue(s)

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)

---

Note

Medium Risk
Changes disposal-rate estimation math in fit(), which drives forecast patterns and full_triangle_; scope is small but actuarially meaningful.

Overview
DisposalRate.fit now converts the input triangle to cumulative (incr_to_cum()) before building disposal_rate_tri and the internal X_ used for development weighting, so disposal rates are cumulative loss ÷ ultimate even when callers pass incremental data.

The sparse test_sparse_transform keeps sample_weight on the sparse backend explicitly when calling fit_transform, matching how production sparse pipelines should pass ultimates.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.27%. Comparing base (0c1830d) to head (6eb6afd).
⚠️ Report is 2 commits behind head on disposal_rate_method.

Additional details and impacted files

@@                   Coverage Diff                    @@
##           disposal_rate_method    #1040      +/-   ##
========================================================
+ Coverage                 89.24%   89.27%   +0.03%     
========================================================
  Files                        91       91              
  Lines                      5233     5233              
  Branches                    666      666              
========================================================
+ Hits                       4670     4672       +2     
+ Misses                      396      393       -3     
- Partials                    167      168       +1     

Flag	Coverage Δ
unittests	89.27% <100.00%> (+0.03%)	⬆️

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