initials derived from name (first + last word), auto
color is a stable hash of the name; explicit color,
image with initials fallback on error, icon fallback without a name
sizes xs · s · m · l · xl (rem-based — density picker scales them)
material-avatar-group max="3" — forces its size onto the
avatars, collapses the rest into +N (hover for names)
RTL — the group stacks mirror