Unwrap <Section/> before handing it to imperative code

Stickers and Emoji opened as three lines of `function () { [native code] }`
and stopped before the sticker packs, on the dev server only. The dev server
wraps every top-level component in a memo for hot reload, so `<Section/>` is a
function there and an element in a production build; the tabs that dropped
SettingSection for `(<Section/>) as HTMLElement` and then appended the value to
the scroll, or reached into it with `appendSectionContent`, got the function.

Every such cast now goes through `unwrapSolidElement` first: Stickers and
Emoji, the chat folder editor, New Group, Add Members (the Mini Apps category of
a privacy exception), a folder's included chats (Chat types) and a shared
folder's invite link. `appendSectionContent` names the cause when it is handed
the memo, or a section with no content element, instead of failing as
`querySelector is not a function`.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>