Forum channels that require tags fail with "A tag is required" when
creating threads because there was no way to pass tag IDs. Add
appliedTags parameter to the thread-create action so forum posts can
include required tags from the channel's available_tags list.
When creating a Discord thread without a messageId (standalone thread),
the Discord API defaults to type 12 (private). Most users expect public.
- Default standalone non-forum threads to ChannelType.PublicThread (11)
- Add optional type field to DiscordThreadCreate for explicit control
Closes#14147
