[CHORE] Move options, deprecations into chainladder._config

[genedan]

Summary of Changes

Moves options and deprecation utilities into a new folder, _config. This is to adhere to the single-responsibility principle. i.e., each module should be responsible for one thing.

The overall package __init__.py is now only responsible for defining the public API - with the exception of the __version__ constant. I didn't have strong feelings about where to put that, and pandas just leaves it in __init__.py. I could move it too, if you want.

Refactored _dask_parallel_warned: bool = False to be a class, this allows it to better maintain state across multiple modules that use it when it's located in a deeper location than __init__.py. This pattern also matches how the Options class maintains the state of its options, to keep things consistent.

Related GitHub Issue(s)

#1145

Additional Context for Reviewers

Made some ruff fixes on existing files.

Checklist

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

---

Note

Low Risk
Mostly a module move with re-exports preserving the public API; small internal state and type-guard changes are covered by existing option/deprecation tests.

Overview
Refactors package configuration out of the top-level chainladder/__init__.py into a new chainladder/_config subpackage (options.py for Options, datetime constants, and options; deprecation.py for backend deprecation helpers and _resolve_pat). The public surface stays the same: cl.options, cl.Options, __dt64_*, and the existing private re-exports on chainladder are unchanged.

ARCHITECTURE.md documents the new _config layout. Minor implementation tweaks: one-time dask parallel deprecation state is now _dask_parallel_state.warned (replacing module-level _dask_parallel_warned), and set_option for ARRAY_BACKEND only warns on deprecated backends when the value is a str.

Tests in test_utilities.py were updated for the new state object and formatted to satisfy ruff (the file’s per-file ignore entry was removed from pyproject.toml).

^{Reviewed by Cursor Bugbot for commit 3f1986c. Bugbot is set up for automated code reviews on this repo. Configure here.}

[github-actions]

Pyright Type Completeness

View the full pyright --verifytypes output for this commit

Project (full chainladder package, at this PR's head): 14.9% of exported symbols fully typed (204 / 1368)

	Known	Ambiguous	Unknown	Total
Project (head)	204	111	1053	1368

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: 325
• Functions without default param: 0
• Classes without docstring: 10

Patch (exported symbols added or changed by this PR): 13 no longer exported

	Known	Ambiguous	Unknown	Total
Patch	0	0	0	0

Patch symbol details

Symbol	Status	Change
chainladder.Options	—	no longer exported (was ❌ unknown)
chainladder.Options.ARRAY_BACKEND	—	no longer exported (was ✅ known)
chainladder.Options.ARRAY_PRIORITY	—	no longer exported (was ✅ known)
chainladder.Options.AUTO_SPARSE	—	no longer exported (was ✅ known)
chainladder.Options.ULT_VAL	—	no longer exported (was ✅ known)
chainladder.Options.__init__	—	no longer exported (was ✅ known)
chainladder.Options.describe_option	—	no longer exported (was ✅ known)
chainladder.Options.get_option	—	no longer exported (was ❌ unknown)
chainladder.Options.reset_option	—	no longer exported (was ✅ known)
chainladder.Options.set_option	—	no longer exported (was ❌ unknown)
chainladder.__dt64_dtype__	—	no longer exported (was ✅ known)
chainladder.__dt64_unit__	—	no longer exported (was ✅ known)
chainladder.options	—	no longer exported (was ❌ unknown)

[codecov]

Codecov Report

❌ Patch coverage is 95.16129% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.70%. Comparing base (5b79e32) to head (3f1986c).

Files with missing lines	Patch %	Lines
chainladder/_config/deprecation.py	85.36%	2 Missing and 4 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1276      +/-   ##
==========================================
+ Coverage   91.68%   91.70%   +0.02%     
==========================================
  Files          93       96       +3     
  Lines        5447     5463      +16     
  Branches      704      704              
==========================================
+ Hits         4994     5010      +16     
  Misses        328      328              
  Partials      125      125              

Flag	Coverage Δ
unittests	91.70% <95.16%> (+0.02%)	⬆️

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[henrydingliu]

a couple small nits. everything else looks good