feat(web): dominant-color accent strip on PlayerBar + bigger Home tiles

#9 — new lib/media/dominantColor.ts: load cover image, downsample to
1x1 canvas, read pixel. Approximates the dominant tone via the
browser's bilinear mean — close enough for an ambient accent without
the 5KB ColorThief dependency. Same-origin cover URLs so no CORS
dance. Result cached by URL so revisits are free.

PlayerBar samples the current track's cover and pipes the resulting
rgb into a 2px accent strip above both the compact and desktop
variants. Transparent until the first resolve; 300ms transition on
colour change so track-skips fade rather than snap.

#10 — slight bump to Home tile widths so a typical viewport shows
roughly 5-6 across instead of cramming 8-9: Playlists w-56, all
remaining AlbumCard rows w-48 (Recently Added + both Rediscover
album scrollers). Replaces the wave-2 sizes that were still showing
7-8 across on wider screens.

web/src/lib/components/PlayerBar.svelte

@@ -13,6 +13,7 @@
   } from '$lib/player/store.svelte';
   import { formatDuration } from '$lib/media/duration';
   import { FALLBACK_COVER, coverUrl } from '$lib/media/covers';
+  import { dominantColorFromUrl, rgbToCssString } from '$lib/media/dominantColor';
   import LikeButton from './LikeButton.svelte';
   import TrackMenu from './TrackMenu.svelte';
 
@@ -44,6 +45,24 @@
   function onCoverError(e: Event) {
     (e.currentTarget as HTMLImageElement).src = FALLBACK_COVER;
   }
+
+  // #9 — dominant-color accent. Sample the current track's cover and
+  // pipe it into a CSS custom property; a 2px strip above the bar
+  // takes on the colour, so the page subtly tracks what's playing.
+  // Cache-backed in dominantColorFromUrl so revisits are free.
+  // Default ('') keeps the strip transparent until the first cover
+  // resolves.
+  let accentRgb = $state('');
+  $effect(() => {
+    const cover = current?.album_id ? coverUrl(current.album_id) : null;
+    if (!cover) {
+      accentRgb = '';
+      return;
+    }
+    dominantColorFromUrl(cover).then((rgb) => {
+      if (rgb) accentRgb = rgbToCssString(rgb);
+    });
+  });
 </script>
 
 {#if current}
@@ -59,6 +78,16 @@
     Play controls maintain 40/48/40 size; like+kebab and column-3 sub-rows
     are shorter so column 2's bottom edge aligns with column 3's bottom.
   -->
+  <!-- Dominant-color accent strip — same colour for both compact
+       and desktop variants, only one renders at a time due to the
+       md: breakpoint switch below. Transparent until the first
+       cover resolves; 300ms tween on colour change so track-skips
+       fade rather than snap. -->
+  <div
+    aria-hidden="true"
+    class="md:hidden h-[2px] w-full transition-colors duration-300"
+    style={accentRgb ? `background-color: ${accentRgb};` : ''}
+  ></div>
   <div
     data-testid="player-bar-compact"
     class="md:hidden flex flex-col gap-1.5 border-t border-border bg-surface px-3 py-2"
@@ -224,6 +253,13 @@
     the redundant PlayerOverflowMenu kebab is no longer mounted (volume,
     shuffle, repeat, queue all live inline in the right cluster).
   -->
+  <!-- See compact-variant accent strip above; desktop has its own
+       so both responsive sizes get the same treatment. -->
+  <div
+    aria-hidden="true"
+    class="hidden md:block h-[2px] w-full transition-colors duration-300"
+    style={accentRgb ? `background-color: ${accentRgb};` : ''}
+  ></div>
   <div
     data-testid="player-bar-desktop"
     class="hidden md:flex md:flex-row md:min-h-[108px] md:items-center md:gap-4 border-t border-border bg-surface md:px-4 md:py-1.5"

web/src/lib/media/dominantColor.ts

@@ -0,0 +1,53 @@
+// Cheap dominant-color extractor: loads an image, draws it scaled
+// to a 1x1 canvas, reads the resulting pixel. The browser's bilinear
+// downsample produces an arithmetic-mean color, which approximates
+// the "dominant" tone close enough for an ambient accent strip.
+// Not aiming for ColorThief-grade clustering — that adds ~5KB and
+// noticeable extraction latency. The user-visible feature is just
+// "the page subtly takes on the current track's hue" and a mean
+// color delivers that.
+//
+// Cover URLs are same-origin (/api/albums/<id>/cover), so no CORS
+// dance is needed. Returns null on any failure (load error, decode
+// error, opaque-canvas getImageData reject) so the caller can fall
+// back to the static accent.
+
+export type Rgb = { r: number; g: number; b: number };
+
+const cache = new Map<string, Promise<Rgb | null>>();
+
+export function dominantColorFromUrl(url: string): Promise<Rgb | null> {
+  const cached = cache.get(url);
+  if (cached) return cached;
+  const p = sample(url);
+  cache.set(url, p);
+  return p;
+}
+
+function sample(url: string): Promise<Rgb | null> {
+  if (typeof window === 'undefined') return Promise.resolve(null);
+  return new Promise((resolve) => {
+    const img = new Image();
+    img.crossOrigin = 'anonymous';
+    img.onload = () => {
+      try {
+        const canvas = document.createElement('canvas');
+        canvas.width = 1;
+        canvas.height = 1;
+        const ctx = canvas.getContext('2d');
+        if (!ctx) return resolve(null);
+        ctx.drawImage(img, 0, 0, 1, 1);
+        const data = ctx.getImageData(0, 0, 1, 1).data;
+        resolve({ r: data[0], g: data[1], b: data[2] });
+      } catch {
+        resolve(null);
+      }
+    };
+    img.onerror = () => resolve(null);
+    img.src = url;
+  });
+}
+
+export function rgbToCssString({ r, g, b }: Rgb): string {
+  return `rgb(${r} ${g} ${b})`;
+}

web/src/routes/+page.svelte

@@ -143,8 +143,9 @@
     >
       {#snippet item(rowItem: PlaylistRowItem)}
         <!-- Playlists at the page anchor: largest of the carousels.
-             Recently added stays at w-44; Rediscover steps down. -->
-        <div class="w-52">
+             Sized so a typical viewport shows ~5-6 across instead
+             of cramming 8-9. -->
+        <div class="w-56">
           {#if rowItem.kind === 'real'}
             <PlaylistCard playlist={rowItem.playlist} />
           {:else}
@@ -174,7 +175,7 @@
           ariaLabel="Recently added"
         >
           {#snippet item(album: import('$lib/api/types').AlbumRef)}
-            <div class="w-44"><AlbumCard {album} /></div>
+            <div class="w-48"><AlbumCard {album} /></div>
           {/snippet}
         </HorizontalScrollRow>
       {/if}