Introduces a new REST API endpoint at `wp-abilities/v1/categories` to expose
ability categories through the WordPress REST API.
The new `WP_REST_Abilities_V1_Categories_Controller` provides:
- GET `/wp-abilities/v1/categories` - Lists all ability categories with pagination
- GET `/wp-abilities/v1/categories/{slug}` - Retrieves a single category by slug
Both endpoints require the `read` capability and return category data including
slug, label, description, and metadata. The collection endpoint supports pagination
with `page` and `per_page` parameters (default: 50, max: 100).
Developed in https://github.com/WordPress/wordpress-develop/pull/10380.
Follow-up [61032].
Props gziolo, jason_the_adams, timothyblynjacobs.
Fixes#64098.
Built from https://develop.svn.wordpress.org/trunk@61045
git-svn-id: http://core.svn.wordpress.org/trunk@60381 1a063a9b-81f0-0310-95a4-ce76da25c4cd
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