fix(tracks): RC3 layout regressions + multi-artist links (#976)

* fix(tracks): RC3 layout regressions + multi-artist links

- Restore vertical rhythm on the Tracks hub: the header/hero/rails/browse
  sections sat two wrapper divs below .tracks-page so its flex gap never
  reached them and they collapsed together. New .tracks-hub-stack re-applies
  the gap, fixing the tagline-touching-hero and Random-Pick-overlapping-hero
  spacing (the rail's nav buttons no longer ride into the box above).
- Stop the sticky browse-table header going transparent on hover: its base
  background became opaque but the :hover rule still forced transparent, so
  rows bled through. Header now keeps its card background on hover.
- Widen the Duration column (56px -> 72px; 56 -> 64 on mobile) so the
  "DURATION" header no longer clips/overruns.
- Split multi-artist tracks into individually clickable artist links in both
  the "Track of the moment" hero and the browse list rows (OpenSubsonic
  artists[] with single-artist fallback), matching the album tracklist.

* docs(changelog): Tracks RC3 spacing, Duration, header hover, multi-artist (#976)

src/styles/tracks/_intro.css

@@ -9,6 +9,16 @@
   padding-bottom: var(--space-8, 2rem);
 }
 
+/* The hub sections (header, hero, rails, browse list) live two wrapper divs
+   deep inside .tracks-page, so the page-level flex gap never reached them and
+   the sections collapsed together. This stack restores even vertical rhythm
+   between them. */
+.tracks-hub-stack {
+  display: flex;
+  flex-direction: column;
+  gap: var(--space-6, 1.5rem);
+}
+
 .tracks-header {
   display: flex;
   align-items: flex-end;

src/styles/tracks/responsive.css

@@ -18,11 +18,11 @@
   }
 
   .song-list-row {
-    grid-template-columns: 64px minmax(0, 1.5fr) minmax(0, 1fr) 56px;
+    grid-template-columns: 64px minmax(0, 1.5fr) minmax(0, 1fr) 64px;
   }
 
   .song-list-row--with-bpm {
-    grid-template-columns: 64px minmax(0, 1.5fr) minmax(0, 1fr) 48px 56px;
+    grid-template-columns: 64px minmax(0, 1.5fr) minmax(0, 1fr) 48px 64px;
   }
 
   .song-list-row-cell:nth-child(4),  /* album */

src/styles/tracks/shared-songrow-used-by-tracks-hub-searchresults-advancedsearch.css

@@ -2,7 +2,7 @@
 
 .song-list-row {
   display: grid;
-  grid-template-columns: 64px minmax(0, 1.5fr) minmax(0, 1fr) minmax(0, 1fr) 110px 56px;
+  grid-template-columns: 64px minmax(0, 1.5fr) minmax(0, 1fr) minmax(0, 1fr) 110px 72px;
   gap: var(--space-3);
   align-items: center;
   height: 52px;
@@ -43,8 +43,11 @@
   border-bottom: 1px solid var(--border-subtle);
 }
 
+/* Header is sticky and opaque — keep its card background on hover so the
+   generic .song-list-row:hover rule doesn't turn it transparent (which let
+   rows scrolling underneath bleed through). */
 .song-list-row--header:hover {
-  background: transparent;
+  background: var(--bg-card);
 }
 
 .song-list-row-cell {
@@ -75,7 +78,7 @@
 }
 
 .song-list-row--with-bpm {
-  grid-template-columns: 64px minmax(0, 1.5fr) minmax(0, 1fr) minmax(0, 1fr) 110px 48px 56px;
+  grid-template-columns: 64px minmax(0, 1.5fr) minmax(0, 1fr) minmax(0, 1fr) 110px 48px 72px;
 }
 
 .song-list-row-bpm {

src/styles/tracks/virtual-song-list.css

@@ -4,7 +4,6 @@
   display: flex;
   flex-direction: column;
   gap: var(--space-3);
-  margin-top: var(--space-2);
 }
 
 .virtual-song-list-title {