Publicize: register WP Abilities API surface

[enejb]

Summary

Registers the first Jetpack Publicize abilities so agents can manage Social via the wp-abilities/v1 REST surface. Gated behind the jetpack_wp_abilities_enabled filter (default false), so this is a no-op until a site opts in.

Three abilities ship in this PR:

• jetpack-publicize/list-connections — read-only, idempotent. Returns the site's connected social accounts as { id, service, external_id, external_name, external_display_name, external_handle, profile_link, profile_picture, status, shared }.
• jetpack-publicize/get-share-status — read-only, idempotent. Returns the share-status snapshot for a published post: { post_id, can_be_shared, done, shares, scheduled_shares }. Mirrors the wpcom/v2/publicize/share-status REST contract.
• jetpack-publicize/delete-connection — destructive but idempotent write. Disconnects a single social account; deleting an already-gone connection returns changed=false. Mirrors the REST controller's delete path.

set-message, schedule-share, and update-share-message are intentionally deferred to a follow-up PR.

Wiring

Publicize_Abilities::init() fires from Publicize_Setup::pre_initialization() (the publicize package's autoloaded bootstrap). Because the Social plugin and the Jetpack plugin (publicize module) both load this package and call pre_initialization() via the Config package, the abilities surface activates in both consumers automatically — no actions.php changes needed. See plan §4.2 / §4.5.

Permissions

• Reads (list-connections, get-share-status): publish_posts. Mirrors the REST publicize_permissions_check intent.
• Write (delete-connection): edit_others_posts. Mirrors Connections_Controller::manage_connection_permission_check's editor+ default. Owner-only deletes aren't exposed at the abilities surface — gating an arbitrary id by ownership before the permission check leaks existence of unowned connections.

Test plan

• composer phpunit -- --filter Publicize_Abilities_Test (36/36 pass, 122 assertions).
• composer phpunit for the full publicize package (114 pass, 4 pre-existing skips).
• composer phpcs:lint on new files clean.
• Changelog entry validated.
• Live-site verification: with add_filter( 'jetpack_wp_abilities_enabled', '__return_true' ), confirm wp_get_abilities() lists the three slugs and /wp-json/wp-abilities/v1/abilities exposes them.

[github-actions]

Are you an Automattician? Please test your changes on all WordPress.com environments to help mitigate accidental explosions.

• To test on WoA, go to the Plugins menu on a WoA dev site. Click on the "Upload" button and follow the upgrade flow to be able to upload, install, and activate the Jetpack Beta plugin. Once the plugin is active, go to Jetpack > Jetpack Beta, select your plugin (Jetpack), and enable the add/ship-publicize-abilities branch.
• To test on Simple, run the following command on your sandbox:

bin/jetpack-downloader test jetpack add/ship-publicize-abilities

Interested in more tips and information?

• In your local development environment, use the jetpack rsync command to sync your changes to a WoA dev blog.
• Read more about our development workflow here: PCYsg-eg0-p2
• Figure out when your changes will be shipped to customers here: PCYsg-eg5-p2

[github-actions]

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[jp-launch-control]

Code Coverage Summary

Coverage changed in 1 file.

File	Coverage	Δ%	Δ Uncovered
projects/packages/publicize/src/class-publicize-setup.php	13/63 (20.63%)	-0.68%	2 ❤️‍🩹

1 file is newly checked for coverage.

File	Coverage
projects/packages/publicize/src/abilities/class-publicize-abilities.php	248/274 (90.51%) 💚

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