Utilize the new client-side Abilities API

[dkotter]

What?

Closes #346

Ensure we properly use the new client-side Abilities API and ensure we fix all errors with existing Abilities

Why?

We currently have a helper method that attempted to use the client-side Abilities API, falling back to making direct API requests if it wasn't available. This was based on the older client-side API and so needed updating with the new version that is shipping with WordPress 7.0 (see post).

In doing this, ran into a number of issues that prevented things from working properly. These issues were silently ignored when using direct API requests but the validation the client-side API uses is more strict and thus surfaced these errors. All of those have been fixed up here.

How?

• Update our runAbility helper function to use the new client-side Abilities API
• Remove the use of sanitize_callback from all of our Ability schemas as this isn't supported by the Abilities API, just the REST API
• Ensure we have proper sanitization ourselves due to the removal of the above
• Ensure the @wordpress/core-abilities script module is loaded anytime an Ability needs it
• Fix an issue where block content was sometimes being returned as an object instead of a string, causing errors with the client-side Abilities API
• Fix some new eslint errors that surfaced after updating dependencies

Use of AI Tools

Used Cursor running GPT-5.3 Codex to figure out how to properly load the @wordpress/core-abilities script module based on our current setup. Also used it to investigate what schema options are supported and verify sanitize_callback was not. All other work done by me

Testing Instructions

1. Pull this PR down and run npm i && npm run build
2. For each Experiment that utilizes AI (everything besides the Abilities Explorer), turn those on one-by-one
3. Test the Experiment you turned on, ensuring you have the browser console open. The Experiment should function the same as it always has and you shouldn't see any errors or messages in the console. Importantly, shouldn't see [AI] Client ability execution unavailable. Falling back to REST.
4. Continuing testing each Experiment ensuring they all still work as expected

[github-actions]

The following accounts have interacted with this PR and/or linked issues. I will continue to update these lists as activity occurs. You can also manually ask me to refresh this list by adding the props-bot label.

If you're merging code through a pull request on GitHub, copy and paste the following into the bottom of the merge commit message.

Co-authored-by: dkotter <dkotter@git.wordpress.org>
Co-authored-by: jeffpaul <jeffpaul@git.wordpress.org>
Co-authored-by: jorgefilipecosta <jorgefilipecosta@git.wordpress.org>
Co-authored-by: gziolo <gziolo@git.wordpress.org>
Co-authored-by: ocean90 <ocean90@git.wordpress.org>

To understand the WordPress project's expectations around crediting contributors, please review the Contributor Attribution page in the Core Handbook.

[codecov]

Codecov Report

❌ Patch coverage is 86.30137% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 65.59%. Comparing base (86b224d) to head (e99ea97).

Files with missing lines	Patch %	Lines
includes/Abilities/Image/Generate_Image.php	57.14%	3 Missing ⚠️
.../Content_Classification/Content_Classification.php	0.00%	1 Missing ⚠️
...eriments/Excerpt_Generation/Excerpt_Generation.php	0.00%	1 Missing ⚠️
.../Experiments/Image_Generation/Image_Generation.php	0.00%	1 Missing ⚠️
.../Experiments/Meta_Description/Meta_Description.php	0.00%	1 Missing ⚠️
includes/Experiments/Review_Notes/Review_Notes.php	0.00%	1 Missing ⚠️
...cludes/Experiments/Summarization/Summarization.php	0.00%	1 Missing ⚠️
.../Experiments/Title_Generation/Title_Generation.php	0.00%	1 Missing ⚠️

Additional details and impacted files

@@              Coverage Diff              @@
##             develop     #364      +/-   ##
=============================================
- Coverage      65.75%   65.59%   -0.16%     
- Complexity       763      771       +8     
=============================================
  Files             53       53              
  Lines           3863     3851      -12     
=============================================
- Hits            2540     2526      -14     
- Misses          1323     1325       +2     

Flag	Coverage Δ
unit	65.59% <86.30%> (-0.16%)	⬇️

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[jeffpaul]

Holding on merge here as its unclear from #346 (comment) whether we should proceed with this PR or await a change in Gutenberg/core that we may then need to adjust for in the AI plugin.

[dkotter]

Making a note for myself that this PR needs updated to account for the newly merged Abilities, namely Content Classification and Meta Descriptions

Edit: Now updated in b3846a1 and e99ea97. If additional Abilities get merged prior to this PR being merged, will update again