bend-lint waits forever when a pending async rule is aborted #1740

lint() checks the abort signal before and after await rule.run(...), but cannot reach the second check while the rule is still pending. An editor cancelling an outdated run can remain stuck forever.

At d194597: start a rule returning a pending promise, wait until its run is entered, then abort the supplied controller. The public lint promise is still waiting; it should reject with the controller’s reason without needing the rule to cooperate.