Human peers surface as raw ids (WhatsApp `…-lid`, UUIDs). Read an
optional `display_name` from peer metadata and prefer it over the id in
the peer header and breadcrumb, with the raw id kept as a sub-caption.
An inline edit on the header writes `display_name` via useUpdatePeer
(merging existing metadata); blank clears it. Falls back to the id when
unset.
Closes#32.