* chore: New feature stubbed out
* feat: Implement createRefund and deleteRefund mutations
createRefund: Creates a refund on an order with amount, reason,
optional payment gateway refund, restock, and meta data support.
Requires edit_shop_orders capability.
deleteRefund: Deletes a refund by ID with optional force flag.
Returns the deleted refund data and parent order.
Requires delete_shop_orders capability.
Both mutations include before/after action hooks for extensibility
and follow the WC REST API refund controller pattern.
Closes#17
* chore: Add PHPStan type annotation for wc_get_order in Refund_Delete
* devops: Add guard tests for deleteRefund mutation
Test invalid refund ID, order ID passed instead of refund ID,
with expectedErrorMessage assertions confirming error messages.
