cancelLastDeviceRecoveryKeyReset

Cancels the pending recovery key reset as this device (a signed request; docs/recovery-key-reset.md). The recovery key and its epoch stay; last-device recovery challenges stay valid.

If reset is no longer pending, returns LastDeviceRecoveryKeyResetCancellationResult.NotPending with the current recovery key status and reset: the same key and epoch mean it was cancelled (by an earlier call whose response was lost, or by another authority); another key means a completion or rotation won. Never recreates a reset.