wp_trim_words - ensure word separation around br tags

[Addison-Stavlo]

Ensures words around br tags are not concatenated together during wp_trim_words by replacing br tags with a space. This is done just before all tags are stripped and will ensure the words are actually separated when the $words_array is generated.

These br tags are common in the core block editor as they can appear in paragraph blocks (shft+enter for spacing), verse blocks, and likely more. For content written in forms similar to that of poetry or song lyrics, excerpts generated from the content stick words together. e.g. "Line one
line two" becomes "line oneline two" - this PR aims to resolve this problem at the source in trim words.

Trac ticket: https://core.trac.wordpress.org/ticket/64944

Use of AI Tools

AI assistance: Yes
Tool(s): Cursor
Model(s): Composer 2
Used for: assistance with initial code investigation, assistance with generating regex pattern, initial test suggestions, and general writing directed by me. Placement of and suggested fix made by me, test reviewed and edited by me.

This Pull Request is for code review only. Please keep all other discussion in the Trac ticket. Do not merge this Pull Request. See GitHub Pull Requests for Code Review in the Core Handbook for more details.

Testing

• Run this branch on WP Playground.
• Create a new post using a paragraph of verse block. For the verse block, standard "enter" to add new lines will repro the issue. For the paragraph block, "shft + enter" to create new lines within the block.
  • You can verify the br tags are separating the lines in these blocks by toggling the code editor setting.
• Do not create a custom excerpt.
• Publish the post.
• Run get_the_excerpt for the post.
• Verify that there are no spaces between the last words of one line and first words of the next. (on trunk, there will be words joined together as described in the examples).

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[github-actions]

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