[FIX] Apply Ruff fix to tutorial and user guide.

[genedan]

Summary of Changes

Stacked PR on top of #1290. Fixes user guide and tutorial 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
Doc-only notebook formatting and lint fixes with no intended change to library behavior or runtime logic.

Overview
Brings getting-started tutorial and user guide Jupyter notebooks in line with the repo’s Ruff lint and format settings, following the broader Ruff rollout (#1216) on top of #1290.

Changes are mechanical in notebook code cells—things like unused import removal, syntax/style fixes covered by the configured rule set, and Ruff formatter layout—across the long-form docs under docs/getting_started/tutorials/ and docs/user_guide/. Example behavior and outputs in the notebooks should be unchanged; this is mainly so CI and pre-commit Ruff checks pass on those doc sources.

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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): 14.9% of exported symbols fully typed (204 / 1369)

	Known	Ambiguous	Unknown	Total
Project (head)	204	110	1055	1369

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: 326
• 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

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.67%. Comparing base (f869370) to head (8d2f02e).

Additional details and impacted files

@@                   Coverage Diff                    @@
##           gd_ruff_fix_adjustments    #1300   +/-   ##
========================================================
  Coverage                    91.67%   91.67%           
========================================================
  Files                           96       96           
  Lines                         5444     5444           
  Branches                       702      702           
========================================================
  Hits                          4991     4991           
  Misses                         332      332           
  Partials                       121      121           

Flag	Coverage Δ
unittests	91.67% <ø> (ø)

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[henrydingliu]

meta comment, do we want to get rid of black in these notebooks now?

[genedan]

meta comment, do we want to get rid of black in these notebooks now?

Yeah, since we switched linters. It's in the Governing Doc so I don't think we need the cell or the paragraph explaining it anymore.