Add the optional A-Z group toggle to the Artists grid (Group: Off/A-Z
QbzSelect, default Off, persisted via favorites_prefs artists_group).
derive_artists now buckets the filtered set into FavArtistSection letter
groups (# first, then A-Z) and builds the alpha-jump model; the grouped grid
renders per-letter headers + sub-grids and an AlphaStrip on the right that
jumps the Flickable proportionally (mirrors the Albums alpha grouping).
Also renames the favorites view header title "Favorites" -> "Library" to
match Qobuz.
cc
vicrodh
41692012ee