fix(nanoplots): keep a stroke width of zero passed to nanoplot_options

[Rodrigo-Palma]

nanoplot_options() takes the default for data_line_stroke_width and vertical_guide_stroke_width with x or default (_helpers.py:1475, _helpers.py:1492), so a width of 0, which is how a caller asks for no stroke at all, reads as "not given":

from great_tables import nanoplot_options

nanoplot_options(data_line_stroke_width=0)["data_line_stroke_width"]  # 8
nanoplot_options(data_line_stroke_width=1)["data_line_stroke_width"]  # 1

Passing 0 produces an SVG byte for byte identical to the default one, so the option is dropped rather than doing something visible that the caller could notice.

The same function already draws this distinction where it matters. Every show_* flag uses True if x is None else x precisely so that False survives, and the widths that go through _normalize_listable_nanoplot_options keep a 0 because it becomes a truthy [0]. These two are the ones left on or.

Reading the default with is None is the smallest change that makes them behave like their neighbours. Colors are left as they are: an empty string is not a value a caller means.

Test run: full pytest tests, 2722 passed, 1 skipped, 6 xfailed. The new test fails on main. ruff check and ruff format --check clean on both files.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.34%. Comparing base (fc46ff9) to head (4a7ff12).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #893   +/-   ##
=======================================
  Coverage   98.34%   98.34%           
=======================================
  Files          52       52           
  Lines        8318     8318           
=======================================
  Hits         8180     8180           
  Misses        138      138           

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[rich-iannone]

LGTM!