Fix /close [soon/immediately] commands not working in threads #21
Description
The commands were implemented with application channels in mind, not application threads.
Instead of scheduling a channel for deletion, a thread should be scheduled (or deleted immediately).
Another question is, if the threads really need to be deleted, since there is no thread count limit I know of (unlike channel count limit). The threads could be locked and/or renamed (prepending them with a fitting emoji like ❌️). This could be useful when the picked voice actor fails to fulfill their obligations in the future and stops providing us with new recordings for updated dialogue – we'll check out these archived/locked threads, see what other voice actors were interested in voicing given NPC and contact one of them, asking them if they're still up to the task.