HTML API: Make get_attribute_names_with_prefix() agree with enqueued attribute updates

[irozum]

get_attribute_names_with_prefix() only looked at the parsed attributes for a tag, so it returned stale data once attributes were set or removed via set_attribute(), remove_attribute(), add_class(), or remove_class(), without first calling get_updated_html(). This brings it in line with get_attribute(), which already reconciles enqueued lexical updates before returning.

Trac ticket: https://core.trac.wordpress.org/ticket/64567

Use of AI Tools

AI assistance: Yes
Tool(s): Claude Code
Model(s): Claude Sonnet 5
Used for: Implementation, debugging (including finding and fixing an attribute-ordering edge case for multiple newly-added attributes), and test coverage.
All changes were reviewed and directed by me throughout.

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[Copilot]

Pull request overview

This PR updates WP_HTML_Tag_Processor::get_attribute_names_with_prefix() so it reflects enqueued attribute changes (from set_attribute(), remove_attribute(), add_class(), remove_class()) even before get_updated_html() is called, aligning its behavior with get_attribute() and fixing stale results (Trac #64567).

Changes:

• Reconcile pending class-name updates into attribute updates before collecting attribute names.
• Include newly-added attribute names from enqueued lexical updates (and exclude attributes enqueued for removal) when filtering by prefix.
• Add PHPUnit coverage for added/removed attributes and class mutations without requiring a prior get_updated_html() call, including a serialized-order assertion for multiple new attributes.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
tests/phpunit/tests/html-api/wpHtmlTagProcessor.php	Adds regression tests covering stale prefix lookups across set/remove attribute and add/remove class flows, including ordering behavior.
src/wp-includes/html-api/class-wp-html-tag-processor.php	Updates get_attribute_names_with_prefix() to account for enqueued updates and adds helper to surface newly-added attribute names in serialized order.

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