[FEAT] Add numeric formatting options

[genedan]

Must approve PR #1276 before this one.

Summary of Changes

• Adds options to pass format string/callable to configure numeric formatting (values and link ratios).
• Makes auto-formatting based on triangle size in Jupyter/HTML output configurable.
• Moves options-related tests to _config folder.

Related GitHub Issue(s)

#1154
#1281
#1283

Additional Context for Reviewers

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

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[codecov]

Codecov Report

❌ Patch coverage is 96.10390% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.74%. Comparing base (660ab7e) to head (a3b258e).
⚠️ Report is 2 commits behind head on main.

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    #1284      +/-   ##
==========================================
+ Coverage   91.68%   91.74%   +0.05%     
==========================================
  Files          93       97       +4     
  Lines        5447     5486      +39     
  Branches      704      706       +2     
==========================================
+ Hits         4994     5033      +39     
  Misses        328      328              
  Partials      125      125              

Flag	Coverage Δ
unittests	91.74% <96.10%> (+0.05%)	⬆️

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[github-actions]

Pyright Type Completeness

View the full pyright --verifytypes output for this commit

Project (full chainladder package, at this PR's head): 14.0% of exported symbols fully typed (189 / 1352)

	Known	Ambiguous	Unknown	Total
Project (head)	189	111	1052	1352

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): 62.5% fully typed (5 / 8); 37 no longer exported

	Known	Ambiguous	Unknown	Total
Patch	5	0	3	8

Patch symbol details

Symbol	Status	Change
chainladder.core.tests.test_display.test_display_option_default_is_none	✅ known	new
chainladder.core.tests.test_display.test_get_format_str_reads_from_options	✅ known	new
chainladder.core.tests.test_display.test_get_format_str_reads_thresholds_from_options	✅ known	new
chainladder.core.tests.test_display.test_normalize_format_passes_through_callable	✅ known	new
chainladder.core.tests.test_display.test_normalize_format_wraps_format_string	✅ known	new
chainladder.core.tests.test_display.test_pattern_format_independent_of_value_format	❌ unknown	new
chainladder.core.tests.test_display.test_value_format_override_affects_heatmap	❌ unknown	new
chainladder.core.tests.test_display.test_value_format_override_affects_repr_and_html	❌ unknown	new
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)
chainladder.utils.tests.test_utilities.test_both_pat_and_option_raises	—	no longer exported (was ✅ known)
chainladder.utils.tests.test_utilities.test_deprecated_option_kwarg_reset_option_warns	—	no longer exported (was ✅ known)
chainladder.utils.tests.test_utilities.test_deprecated_option_kwarg_warns	—	no longer exported (was ✅ known)
chainladder.utils.tests.test_utilities.test_describe_option	—	no longer exported (was ✅ known)
chainladder.utils.tests.test_utilities.test_describe_option_all	—	no longer exported (was ❌ unknown)
chainladder.utils.tests.test_utilities.test_describe_option_invalid	—	no longer exported (was ✅ known)
chainladder.utils.tests.test_utilities.test_describe_option_invalid_regex	—	no longer exported (was ✅ known)
chainladder.utils.tests.test_utilities.test_describe_option_multi	—	no longer exported (was ❌ unknown)
chainladder.utils.tests.test_utilities.test_describe_option_no_docstring_match	—	no longer exported (was ✅ known)
chainladder.utils.tests.test_utilities.test_describe_option_return_string	—	no longer exported (was ✅ known)
chainladder.utils.tests.test_utilities.test_get_option	—	no longer exported (was ✅ known)
chainladder.utils.tests.test_utilities.test_get_option_missing_pat_raises	—	no longer exported (was ✅ known)
chainladder.utils.tests.test_utilities.test_options_defaults	—	no longer exported (was ✅ known)
chainladder.utils.tests.test_utilities.test_reset_option	—	no longer exported (was ✅ known)
chainladder.utils.tests.test_utilities.test_reset_option_invalid	—	no longer exported (was ✅ known)
chainladder.utils.tests.test_utilities.test_reset_single_option	—	no longer exported (was ✅ known)
chainladder.utils.tests.test_utilities.test_set_option_consistency	—	no longer exported (was ✅ known)
chainladder.utils.tests.test_utilities.test_set_option_cupy_backend_deprecated	—	no longer exported (was ✅ known)
chainladder.utils.tests.test_utilities.test_set_option_cupy_priority_deprecated	—	no longer exported (was ✅ known)
chainladder.utils.tests.test_utilities.test_set_option_dask_backend_deprecated	—	no longer exported (was ✅ known)
chainladder.utils.tests.test_utilities.test_set_option_dask_priority_deprecated	—	no longer exported (was ✅ known)
chainladder.utils.tests.test_utilities.test_set_option_deprecated_priority_last_no_warning	—	no longer exported (was ❌ unknown)
chainladder.utils.tests.test_utilities.test_set_option_missing_value_raises	—	no longer exported (was ✅ known)
chainladder.utils.tests.test_utilities.test_set_option_supported_backend_no_warning	—	no longer exported (was ❌ unknown)