Fix/query default posts per page

[pranvinit]

What?

Closes #77886

Allows the Query Loop block’s default query type to override “Items per page”.

Why?

Default Query Loop blocks inherit the current template query, but users could not reduce the number of displayed posts for archive templates without custom code.

How?

Shows the “Items per page” control for inherited queries and applies query.perPage when rendering inherited Query Loop results, pagination, totals, and no-results state.

Testing Instructions

1. Set Settings > Reading > Blog pages show at most to 10.
2. Create or edit an author archive template.
3. Add a Query Loop block using the Default query type.
4. Set Items per page to 3.
5. Confirm the template shows 3 posts while still filtering to the current author.

Testing Instructions for Keyboard

1. Select the Query Loop block.
2. Use keyboard navigation to open the block inspector.
3. Set Query type to Default.
4. Navigate to Display > Items per page and change the value.
5. Confirm the setting updates and remains usable by keyboard.

Screenshots or screencast

N/A

Use of AI Tools

AI tooling was used to help draft and implement the change. The code was reviewed before submission.

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Co-authored-by: pranvinit <pranavyeole@git.wordpress.org>
Co-authored-by: Mamaduka <mamaduka@git.wordpress.org>
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[Mamaduka]

Thanks for the PR, @pranvinit!

The referenced issue isn't a bug, at least not as the Query block currently works. Default queries will use per_page from settings, which is usually 10.