[ryanchou1994]

Long headings are passed through the paragraph wrapper, so everything after the first wrapped line becomes ordinary text in the generated Markdown. For example, <h1>A long heading with several words</h1> should keep its whole title after #, even when body_width is small.

Skip wrapping ATX heading lines, including headings inside blockquotes. The matcher uses ASCII spaces and tabs so ordinary text containing non-breaking spaces keeps its existing wrapping behavior. Paragraphs, hashtags, and lines with seven # characters still wrap normally.

The regression fixture exercises the class, convenience function, and actual CLI, including emphasis and inline links in headings. Additional tests cover h1–h6, quoted headings, wrapping disabled, and three Unicode-whitespace controls. This change addresses wrapping added by body_width; it does not change explicit line breaks already present inside a heading or implement a full Markdown parser.

Validation: 241 tests each on macOS (Python 3.13.13) and Linux (Python 3.13.15), plus Black, Flake8, isort, strict mypy 1.19.1 (Python 3.9 target), wheel/sdist builds and Twine checks. The installed Linux wheel passed 12 API/CLI checks outside the checkout. The existing generator-parametrization warnings from pytest remain. One existing expression in the touched config file was reformatted by Black 26.5.1.

Fixes #424

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