sync

[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

Low Risk
Small refactor plus I/O test coverage; Development keeps its own three-argument _param_property, so incremental behavior should follow the moved helper unchanged.

Overview
Triangle pickle I/O is documented at the module level in chainladder/core/io.py, with imports reordered and an unused joblib import dropped from that file (pickling still uses dill).

Development estimators: _param_property is added as a static helper on DevelopmentBase, and the duplicate implementation is removed from IncrementalAdditive, which now calls the shared helper for zeta_. Type hints in DevelopmentBase switch from TriangleLike to Triangle for _set_fit_groups.

Tests: test_triangle_to_pickle exercises Triangle.to_pickle / read_pickle round-trips for single- and multi-dimensional sample triangles (raa, clrd).

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 89.38%. Comparing base (b6e8349) to head (468f11a).
⚠️ Report is 29 commits behind head on disposal_rate_method.

Additional details and impacted files

@@                   Coverage Diff                    @@
##           disposal_rate_method    #1041      +/-   ##
========================================================
+ Coverage                 89.17%   89.38%   +0.20%     
========================================================
  Files                        89       91       +2     
  Lines                      5165     5266     +101     
  Branches                    661      678      +17     
========================================================
+ Hits                       4606     4707     +101     
+ Misses                      392      391       -1     
- Partials                    167      168       +1     

Flag	Coverage Δ
unittests	89.38% <100.00%> (+0.20%)	⬆️

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