feat: leave the Laravel queue out of auto until a connection is set for async actions

[ogorzalka]

Follow-up to #427: the Laravel queue becomes opt-in for auto.

Why. The skeleton ships QUEUE_CONNECTION=database. With the queue first in auto (as #427 did, following the design doc), every async action of a default Pollora project went to the database queue and waited for a worker. On hosting without one, handlers never ran, with no error anywhere. A handler that silently never runs is the worst failure mode. The framework already treats the Laravel scheduler as opt-in (wordpress.use_laravel_scheduler), so this is consistent.

Now.

• auto puts the queue first only when hooks.async.queue.connection (HOOKS_ASYNC_CONNECTION) names the connection a worker runs. A sync or null connection is still skipped.
• Without it, auto picks Action Scheduler, then WP-Cron, which run without any extra process.
• via('queue'), #[Async(via: 'queue')] and HOOKS_ASYNC_DRIVER=queue still use the default connection: an explicit choice.
• config/hooks.php and the CHANGELOG explain it. The design doc is updated.

Tests. The provider test covers "no connection set: wp-cron despite a database default connection", "set: queue", and "set to sync: skipped". The E2E spec uses via: 'queue' and is unaffected.