Try 2: Add get and post/pages abilities.

src/wp-includes/abilities-api/class-wp-abilities-registry.php

@@ -78,11 +78,11 @@ final class WP_Abilities_Registry {
 	 * @return WP_Ability|null The registered ability instance on success, null on failure.
 	 */
 	public function register( string $name, array $args ): ?WP_Ability {
-		if ( ! preg_match( '/^[a-z0-9-]+\/[a-z0-9-]+$/', $name ) ) {
+		if ( ! preg_match( '/^[a-z0-9-]+(?:\/[a-z0-9-]+)+$/', $name ) ) {
 			_doing_it_wrong(
 				__METHOD__,
 				__(
-					'Ability name must be a string containing a namespace prefix, i.e. "my-plugin/my-ability". It can only contain lowercase alphanumeric characters, dashes and the forward slash.'
+					'Ability name must be a string containing a namespace prefix, e.g. "my-plugin/my-ability" or "my-plugin/my-namespace/my-ability". It can only contain lowercase alphanumeric characters, dashes and forward slashes as separators.'
 				),
 				'6.9.0'
 			);

src/wp-includes/abilities.php

@@ -9,6 +9,8 @@
 
 declare( strict_types = 1 );
 
+require_once __DIR__ . '/abilities/class-wp-post-type-abilities.php';
+
 /**
  * Registers the core ability categories.
  *
@@ -32,6 +34,14 @@ function wp_register_core_ability_categories(): void {
 			'description' => __( 'Abilities that retrieve or modify user information and settings.' ),
 		)
 	);
+
+	wp_register_ability_category(
+		'post',
+		array(
+			'label'       => __( 'Post' ),
+			'description' => __( 'Abilities related to the creation and management of posts of all types.' ),
+		)
+	);
 }
 
 /**
@@ -259,4 +269,6 @@ function wp_register_core_abilities(): void {
 			),
 		)
 	);
+
+	WP_Post_Type_Abilities::register();
 }