ChannelControl (add Public/Hashtag/Private, rename, delete, notif/fav/scope)
and Favourites slots move into ui-core; ui-new uses them. Contact / channel
pref cleanup moves from ui-new's UITask into UiCore so it runs on every
frontend (L2 had none). L2: channel options popup (hold a row or the gear
in a channel) and the Add / Edit channel form.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>