Mirrors the web equivalents at the same ~176dp width so the home
Playlists row keeps visual rhythm whether the slot is filled with a
real playlist or a placeholder.
PlaylistPlaceholderCard variants:
- building: spinner + "Building…"
- failed: warning + "Couldn't generate"
- seed-needed: muted icon + "Like more music"
- pending: muted icon + "Coming soon"
Used in the next commit's home Playlists row; otherwise unused this
slice.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
