[FEAT] Catch and speak dialog for unavailable devices

[NeonDaniel]

Currently, a confirmation is spoken when a command is sent which does not account for a disabled device or one that is offline/temporarily inaccessible. It would generally be more helpful to speak that the command was not handled or something to notify the user that the command was understood but nothing happened.

It may also be possible to fall back to the next closest match in the event the requested device is disabled. I think in general though its up to the user to manage which HomeAssistant devices are exposed to Assist.