Changes

• Message.php: When a string is passed as $role that doesn't match any MessageRole enum case, MessageRole::tryFrom($role) returns null and was assigned to the non-nullable $role property, causing a TypeError. Now throws InvalidArgumentException('Invalid message role.') with a clear message.

• HandlesRateLimiting.php: RequestException can have a null response when the request never completed (e.g. connection timeout, DNS failure). Accessing $e->response->status() without a check could cause a null dereference. Now checks $e->response !== null before reading ->status().