[FIX] Apply Ruff fix to chainladder/tails.

[genedan]

Summary of Changes

Stacked PR on #1290. Fixes chainladder/tails files.

Related GitHub Issue(s)

#1216

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

Low Risk
Formatting and lint-only edits to tail reserving code; no intended algorithm or API changes beyond equivalent type checks.

Overview
Applies Ruff lint and format cleanup across chainladder/tails/base.py, bondy.py, and curve.py so those modules meet the project rules without per-file ignores.

Changes are mostly mechanical: docstring/layout formatting, spacing around operators and dict literals, double-quoted strings, and wrapping long lines. TailBondy drops an unused DevelopmentBase import; TailCurve removes an unused num_to_nan import and replaces type(...) == slice with type(...) is slice for the deprecated fit_period slice path.

pyproject.toml removes the Ruff per-file-ignores entries for the three tail files now that they pass the selected rules.

^{Reviewed by Cursor Bugbot for commit e9a0dd8. 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): 15.4% of exported symbols fully typed (213 / 1381)

	Known	Ambiguous	Unknown	Total
Project (head)	213	111	1057	1381

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): no exported symbol type-completeness changes detected.

[codecov]

Codecov Report

❌ Patch coverage is 82.35294% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.66%. Comparing base (198832c) to head (e9a0dd8).

Files with missing lines	Patch %	Lines
chainladder/tails/curve.py	57.14%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@                   Coverage Diff                   @@
##           gd_ruff_fix_methods    #1296      +/-   ##
=======================================================
- Coverage                91.66%   91.66%   -0.01%     
=======================================================
  Files                       93       93              
  Lines                     5437     5436       -1     
  Branches                   704      704              
=======================================================
- Hits                      4984     4983       -1     
  Misses                     328      328              
  Partials                   125      125              

Flag	Coverage Δ
unittests	91.66% <82.35%> (-0.01%)	⬇️

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