Check REST visibility for content resizing posts

[yusufhay]

What?

Adds a REST visibility check to the Content Resizing ability permission callback when a post ID is supplied.

Why?

Similar text abilities already prevent execution for posts whose post type is not exposed in REST. Content Resizing checked whether the user could edit the post, but did not apply that post type visibility check, leaving the ability inconsistent with the rest of the plugin.

How?

After confirming the post exists and the current user can edit it, the permission callback now checks the post type and returns false if the post type is missing or not exposed in REST.

Use of AI Tools

AI assistance: Yes
Tool(s): Codex / ChatGPT
Model(s): GPT-5
Used for: Comparing permission callbacks across similar abilities and drafting the consistency fix. I reviewed the change and PR description before submitting.

Testing Instructions

1. Install and activate this PR build of the AI plugin.
2. Enable the Content Resizing experiment.
3. Open a normal REST-exposed post type, such as a post, and confirm content resizing still works for editable content.
4. Register or use a post type that is not exposed in REST.
5. Attempt to run the Content Resizing ability with a post ID from that post type.
6. Confirm permission is denied instead of allowing the ability to run.

Screenshots or screencast

Not applicable. This PR does not change the UI.

Changelog Entry

Fixed - Restrict content resizing to REST-exposed post types when a post ID is provided.

[github-actions]

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Co-authored-by: yusufhay <yusufmudagal@git.wordpress.org>
Co-authored-by: dkotter <dkotter@git.wordpress.org>

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.75%. Comparing base (64e8032) to head (31193b2).
⚠️ Report is 2 commits behind head on develop.

Additional details and impacted files

@@              Coverage Diff              @@
##             develop     #658      +/-   ##
=============================================
+ Coverage      74.57%   74.75%   +0.17%     
- Complexity      1754     1755       +1     
=============================================
  Files             85       85              
  Lines           7548     7553       +5     
=============================================
+ Hits            5629     5646      +17     
+ Misses          1919     1907      -12     

Flag	Coverage Δ
unit	74.75% <100.00%> (+0.17%)	⬆️

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[dkotter]

There are a handful of PHPCS and PHPStan errors here that need cleaned up before we merge this