Replaces WP_HTTP_Polling_Sync_Server with
WP_HTTP_Polling_Collaboration_Server using the wp-collaboration/v1
REST namespace. Switches to string-based client IDs, fixes the
compaction race condition, adds a backward-compatible wp-sync/v1
route alias, and uses UPDATE-then-INSERT for awareness data.

Deletes WP_Sync_Post_Meta_Storage and WP_Sync_Storage interface,
and removes the wp_sync_storage post type registration from post.php.
These are superseded by the dedicated collaboration table.

Adds wp_is_collaboration_enabled() gate, injects the collaboration
setting into the block editor, registers cron event for cleaning up
stale collaboration data, and updates require/include paths for the
new storage and server classes.

Adds 67 PHPUnit tests for WP_HTTP_Polling_Collaboration_Server covering
document sync, awareness, undo/redo, compaction, permissions, cursor
mechanics, race conditions, cron cleanup, and the backward-compatible
wp-sync/v1 route. Adds E2E tests for 3-user presence, sync, and
undo/redo. Removes the old sync server tests. Updates REST schema
setup and fixtures for the new collaboration endpoints.

Restore the `wp_client_side_media_processing_enabled` filter and the
`finalize` route that were accidentally removed from the REST schema
test. Add the `collaboration` table to the list of tables expected to
be empty after multisite site creation.

The connectors API key entries in wp-api-generated.js were
incorrectly carried over during the trunk merge. Trunk does not
include them in the generated fixtures since the settings are
dynamically registered and not present in the CI test context.

Add a composite index on (type, client_id) to the collaboration table
to speed up awareness upserts, which filter on both columns.

Bump $wp_db_version from 61840 to 61841 so existing installations
pick up the schema change via dbDelta on upgrade.

Reject non-numeric object IDs early in
can_user_collaborate_on_entity_type(). Verify that a post's actual
type matches the room's claimed entity name before granting access.

For taxonomy rooms, confirm the term exists in the specified taxonomy
and simplify the capability check to use assign_term with the
term's object ID.

Cover oversized request body (413), exceeding max rooms (400),
non-numeric object ID, post type mismatch, nonexistent taxonomy
term, and term in the wrong taxonomy.

When collaboration is disabled, run both DELETE queries (sync and
awareness rows) before unscheduling the cron hook so leftover data
is removed. Hoist `global $wpdb` to the top of the function so the
disabled branch can use it. Add a comment noting future persistent
types may also need exclusion from the sync cleanup query.

…rage.php

Co-authored-by: Peter Wilson <519727+peterwilsoncc@users.noreply.github.com>

Co-authored-by: Peter Wilson <519727+peterwilsoncc@users.noreply.github.com>

…d option name

…e extensibility

…nario methods

…n fix

…ordpress-develop into collaboration/single-table