fix(slint): follow chip, playlist card size, track row hover, dedupe

- Follow button on the artist card is no longer a pill — Radius.sm
  rounded rectangle, matching the rest of the app (new ADR-008).
- PlaylistCard sized identically to AlbumCard (220x266) with the same
  220px artwork area; collage and the grid/carousel updated to match.
- Track row play overlay now appears anywhere over the row, not only
  when the pointer is directly over the cell. Slint does not propagate
  has-hover to ancestor TouchAreas, so each row OR-s its own ta with
  every nested TouchArea (play-cell, fav/dl/more) into row-hovered.
- EqualizerBars sit on a fixed 16px baseline so the animation stays
  perfectly centered while the bar heights oscillate.
- TrackPlayCell exposes out hovered so rows can OR it cleanly.
- Search dedupes a top-result artist that is also the first carousel
  entry, removing the redundant duplicate.

cc

crates/qbz-slint/ui/discover/ArtistCard.slint

@@ -4,6 +4,7 @@
 
 import { Theme } from "../foundation/semantic-colors.slint";
 import { Typography } from "../foundation/typography.slint";
+import { Radius } from "../foundation/radius.slint";
 import { SlimItem } from "../state.slint";
 import { QbzIcon } from "../primitives/QbzIcon.slint";
 
@@ -74,7 +75,9 @@ export component ArtistCard inherits Rectangle {
             Rectangle {
                 width: chip-row.preferred-width;
                 height: 30px;
-                border-radius: 15px;
+                // Rectangular with small rounded corners — QBZ never uses
+                // pill-shaped chips (ADR-008).
+                border-radius: Radius.sm;
                 background: follow-ta.has-hover
                     ? Theme.surface-hover
                     : Theme.surface-elevated;