Add an AlphaStrip overlaid on the right edge when grouping
alphabetically: tracks "Group: Name" (jumps the virtualized ListView to
the first row of a letter — accurate, uniform 50px rows) and albums
"Group: A-Z" (jumps the grid Flickable proportionally by section ordinal
— approximate, always lands the section in view, per the agreed
ArtistView-style behavior). derive_tracks/derive_albums build the
per-letter jump model (tracks-alpha / albums-alpha).
cc
vicrodh
dbd6d2e4b5