Replace <em> with <span> for desc_annotation semantic HTML

[q2mark]

Purpose

This PR replaces <em class="property"> with <span class="property"> in the HTML5 writer's visit_desc_annotation and depart_desc_annotation methods to improve semantic HTML structure for Python attribute type annotations.

Changes:

• Modified sphinx/writers/html5.py to use <span> instead of <em> tags while maintaining the existing property CSS class
• Updated corresponding test expectations in tests/test_domains/test_domain_py_pyobject.py

Benefits:

• Improves semantic HTML structure
• Prevents unintended visual styling of punctuation and type information
• Enhances accessibility for screen readers

The change maintains all existing functionality and CSS styling while providing better semantic meaning.

References

• Fixes Python attribute type annotations use inappropriate <em> tags, breaking semantic HTML #13688

[AA-Turner]

Hi @q2mark this commit has the author of "Claude". Please confirm that this PR is entirely comprised of your own work, and you posses the legal right to copyright.

A

[q2mark]

Hi @q2mark this commit has the author of "Claude". Please confirm that this PR is entirely comprised of your own work, and you posses the legal right to copyright.

A

@AA-Turner yes this is entirely my own work and I have the right to copyright.

[AA-Turner]

Do you have a suggested link / reference for "semantic HTML structure"?

Suggested change

	* #13688: HTML5: Replace ``<em class="property">`` with ``<span class="property">``
	for Python attribute type annotations to improve semantic HTML structure.
	Patch by Mark O.
	* #13688: HTML builder: Replace ``<em class="property">`` with ``<span class="property">``
	for Python attribute type annotations to improve semantic HTML structure.
	Patch by Mark Ostroth.

[q2mark]

@AA-Turner this is the current reference for all HTML elements.

https://html.spec.whatwg.org/multipage/text-level-semantics.html

Or MDN: https://developer.mozilla.org/en-US/docs/Web/HTML/Reference/Elements

Turns out we might want to use "var" and "code" but that could break existing themes. For now I am suggesting removing <em> because the intention is not to emphasize text but to denote the purpose of the code.

[AA-Turner]

Oh, please also add yourself to AUTHORS.

[q2mark]

Oh, please also add yourself to AUTHORS.

Done.