…eries

- Remove get_objects_in_term fallback from get_all_friend_users(); feeds
  now exclusively use wp_term_taxonomy.parent to link to subscriptions
- Add hierarchical => true to feed taxonomy registration so parent queries work
- Add hide_empty => false to all User_Feed term queries (get_by_url,
  get_all_users, get_all_due, get_by_parser) since feed terms have count=0
  in the new parent-based approach
- Update test-feed.php to use User::create() instead of WP user factory,
  matching the Subscription-based architecture

- test_convert_friend_user_to_subscription: verifies Subscription::convert_from_user()
  migrates feeds (parent set via direct SQL), posts (author=0, subscription term),
  and user options from a WP-user-backed friend to a virtual subscription
- test_convert_friend_users_batch: verifies the batch migration finds users with
  old friend/acquaintance roles and converts them all to subscriptions
- test_link_feeds_as_term_children: verifies the batch that converts pre-existing
  object_terms feed relationships (subscription_term_id → feed_term) to the new
  parent-based hierarchy, and removes the old term_relationships entries

Note: wp_cache_flush() is required after these migrations in tests because the
direct SQL updates bypass WordPress's object cache; in production this is not an
issue since migrations run in a cron/batch context before the next page request.

Remote_Actors::get_by_uri() returns a WP_Post, not an Actor object.
Pass it through get_actor() to get the Actor with get_image()/get_summary().

In multisite, delete() calls remove_user_from_blog() rather than
wp_delete_user(), so the user still exists network-wide. Check that the
user is either deleted or no longer a member of the current blog.

The direct $wpdb->query UPDATE on term_taxonomy.parent doesn't invalidate
WordPress term caches, causing get_feeds() to return stale results.

…sion

The delete_user hook in Admin::delete_user() finds feeds via object_id-based
term relationships and deletes them. Since convert_from_user sets the parent
but leaves the old term_relationships intact, the subsequent user deletion
would delete the just-migrated feeds. Remove the old relationships after
re-parenting to prevent this.

wp_remove_object_terms() triggers WordPress hooks that cause side effects
breaking the migration. Use a direct $wpdb DELETE instead, followed by
clean_term_cache to invalidate stale caches. This also prevents the
Admin::delete_user hook from finding and deleting the just-migrated feeds
(which only happened for users with the subscription capability).

Private URL authentication was part of the removed friendship
functionality. Replace all get_private_url() calls with get_url().

Add a test that verifies cron_friends_refresh_feeds() can resolve
the friend user via parent term and create posts — the flow that
was broken by the stale access_control reference.