refactor: extract Qobuz adapters and unify DisplayTrack type

- Create $lib/adapters/qobuzAdapters.ts with:
  - formatDuration/formatDurationMinutes (removed duplicates)
  - getQobuzImage helper
  - formatQuality/formatAlbumQuality helpers
  - convertQobuzAlbum converter
  - convertQobuzArtist converter

- Add unified DisplayTrack type to $lib/types/index.ts

- Update +page.svelte:
  - Import adapters instead of inline functions
  - Remove duplicate converter functions (−57 lines)
  - Add handleDisplayTrackPlay for view components

- Fix TypeScript type narrowing in view closures

src/lib/adapters/qobuzAdapters.ts

@@ -0,0 +1,138 @@
+/**
+ * Qobuz Adapters
+ *
+ * Centralizes Qobuz API -> UI model conversion functions.
+ * Eliminates duplicate formatting logic across the codebase.
+ */
+
+import type {
+  QobuzAlbum,
+  QobuzArtist,
+  AlbumDetail,
+  ArtistDetail
+} from '$lib/types';
+
+// ============ Formatting Utilities ============
+
+/**
+ * Format duration in seconds to "M:SS" format
+ */
+export function formatDuration(seconds: number): string {
+  const mins = Math.floor(seconds / 60);
+  const secs = Math.floor(seconds % 60);
+  return `${mins}:${secs.toString().padStart(2, '0')}`;
+}
+
+/**
+ * Alias for formatDuration (they were identical)
+ */
+export const formatDurationMinutes = formatDuration;
+
+/**
+ * Extract best available image from Qobuz image object
+ */
+export function getQobuzImage(image?: { large?: string; thumbnail?: string; small?: string }): string {
+  return image?.large || image?.thumbnail || image?.small || '';
+}
+
+/**
+ * Format quality string from bit depth and sampling rate
+ */
+export function formatQuality(
+  hires: boolean | undefined,
+  bitDepth: number | undefined,
+  samplingRate: number | undefined
+): string {
+  if (hires && bitDepth && samplingRate) {
+    return `${bitDepth}bit/${samplingRate}kHz`;
+  }
+  return 'CD Quality';
+}
+
+/**
+ * Format album quality string (different format with dash)
+ */
+export function formatAlbumQuality(
+  hires: boolean | undefined,
+  bitDepth: number | undefined,
+  samplingRate: number | undefined
+): string {
+  if (hires && bitDepth && samplingRate) {
+    return `${bitDepth}-Bit / ${samplingRate} kHz`;
+  }
+  return 'CD Quality';
+}
+
+// ============ Model Converters ============
+
+/**
+ * Convert Qobuz API album response to UI AlbumDetail model
+ */
+export function convertQobuzAlbum(album: QobuzAlbum): AlbumDetail {
+  const artwork = getQobuzImage(album.image);
+  const quality = formatAlbumQuality(
+    album.hires_streamable,
+    album.maximum_bit_depth,
+    album.maximum_sampling_rate
+  );
+
+  return {
+    id: album.id,
+    artwork,
+    title: album.title,
+    artist: album.artist?.name || 'Unknown Artist',
+    artistId: album.artist?.id,
+    year: album.release_date_original?.split('-')[0] || '',
+    label: album.label?.name || '',
+    genre: album.genre?.name || '',
+    quality,
+    trackCount: album.tracks_count || album.tracks?.items?.length || 0,
+    duration: formatDuration(album.duration || 0),
+    tracks: album.tracks?.items?.map((track, index) => ({
+      id: track.id,
+      number: index + 1,
+      title: track.title,
+      artist: track.performer?.name,
+      duration: formatDuration(track.duration),
+      durationSeconds: track.duration,
+      quality: track.hires_streamable ? 'Hi-Res' : 'CD',
+      hires: track.hires_streamable,
+      bitDepth: track.maximum_bit_depth,
+      samplingRate: track.maximum_sampling_rate,
+      albumId: album.id,
+      artistId: track.performer?.id ?? album.artist?.id,
+      isrc: track.isrc
+    })) || []
+  };
+}
+
+/**
+ * Convert Qobuz API artist response to UI ArtistDetail model
+ */
+export function convertQobuzArtist(artist: QobuzArtist): ArtistDetail {
+  const image = getQobuzImage(artist.image);
+
+  return {
+    id: artist.id,
+    name: artist.name,
+    image,
+    albumsCount: artist.albums_count,
+    biography: artist.biography,
+    albums: artist.albums?.items?.map(album => {
+      const artwork = getQobuzImage(album.image);
+      const quality = formatQuality(
+        album.hires_streamable,
+        album.maximum_bit_depth,
+        album.maximum_sampling_rate
+      );
+      return {
+        id: album.id,
+        title: album.title,
+        artwork,
+        year: album.release_date_original?.split('-')[0],
+        quality
+      };
+    }) || [],
+    totalAlbums: artist.albums?.total || artist.albums_count || 0
+  };
+}

src/lib/components/views/AlbumDetailView.svelte

@@ -247,7 +247,7 @@
             onShareQobuz: onTrackShareQobuz ? () => onTrackShareQobuz(track.id) : undefined,
             onShareSonglink: onTrackShareSonglink ? () => onTrackShareSonglink(track) : undefined,
             onGoToAlbum: onTrackGoToAlbum ? () => onTrackGoToAlbum(album.id) : undefined,
-            onGoToArtist: album.artistId && onTrackGoToArtist ? () => onTrackGoToArtist(album.artistId) : undefined
+            onGoToArtist: album.artistId && onTrackGoToArtist ? () => onTrackGoToArtist(album.artistId!) : undefined
           }}
         />
       {/each}

src/lib/components/views/ArtistDetailView.svelte

@@ -289,8 +289,8 @@
                   onAddToPlaylist={onTrackAddToPlaylist ? () => onTrackAddToPlaylist(track.id) : undefined}
                   onShareQobuz={onTrackShareQobuz ? () => onTrackShareQobuz(track.id) : undefined}
                   onShareSonglink={onTrackShareSonglink ? () => onTrackShareSonglink(track) : undefined}
-                  onGoToAlbum={track.album?.id && onTrackGoToAlbum ? () => onTrackGoToAlbum(track.album.id) : undefined}
-                  onGoToArtist={(track.performer?.id || artist.id) && onTrackGoToArtist ? () => onTrackGoToArtist(track.performer?.id || artist.id) : undefined}
+                  onGoToAlbum={track.album?.id && onTrackGoToAlbum ? () => onTrackGoToAlbum(track.album!.id) : undefined}
+                  onGoToArtist={(track.performer?.id || artist.id) && onTrackGoToArtist ? () => onTrackGoToArtist(track.performer?.id ?? artist.id) : undefined}
                 />
               </div>
             </div>

src/lib/components/views/PlaylistDetailView.svelte

@@ -640,8 +640,8 @@
               onAddToPlaylist: !track.isLocal && onTrackAddToPlaylist ? () => onTrackAddToPlaylist(track.id) : undefined,
               onShareQobuz: !track.isLocal && onTrackShareQobuz ? () => onTrackShareQobuz(track.id) : undefined,
               onShareSonglink: !track.isLocal && onTrackShareSonglink ? () => onTrackShareSonglink(track) : undefined,
-              onGoToAlbum: !track.isLocal && track.albumId && onTrackGoToAlbum ? () => onTrackGoToAlbum(track.albumId) : undefined,
-              onGoToArtist: !track.isLocal && track.artistId && onTrackGoToArtist ? () => onTrackGoToArtist(track.artistId) : undefined
+              onGoToAlbum: !track.isLocal && track.albumId && onTrackGoToAlbum ? () => onTrackGoToAlbum(track.albumId!) : undefined,
+              onGoToArtist: !track.isLocal && track.artistId && onTrackGoToArtist ? () => onTrackGoToArtist(track.artistId!) : undefined
             }}
           />
           {#if track.isLocal}

src/lib/components/views/SearchView.svelte

@@ -393,8 +393,8 @@
                   onAddToPlaylist={onTrackAddToPlaylist ? () => onTrackAddToPlaylist(track.id) : undefined}
                   onShareQobuz={onTrackShareQobuz ? () => onTrackShareQobuz(track.id) : undefined}
                   onShareSonglink={onTrackShareSonglink ? () => onTrackShareSonglink(track) : undefined}
-                  onGoToAlbum={track.album?.id && onTrackGoToAlbum ? () => onTrackGoToAlbum(track.album.id) : undefined}
-                  onGoToArtist={track.performer?.id && onTrackGoToArtist ? () => onTrackGoToArtist(track.performer.id) : undefined}
+                  onGoToAlbum={track.album?.id && onTrackGoToAlbum ? (() => { const albumId = track.album!.id!; return () => onTrackGoToAlbum(albumId); })() : undefined}
+                  onGoToArtist={track.performer?.id && onTrackGoToArtist ? (() => { const artistId = track.performer!.id!; return () => onTrackGoToArtist(artistId); })() : undefined}
                 />
               </div>
             </div>

src/lib/types/index.ts

@@ -134,6 +134,30 @@ export interface PlaylistTrack {
   isrc?: string;
 }
 
+/**
+ * Unified display track interface used across views
+ * Compatible with PlaylistTrack, FavoritesTrack, and ArtistTrack displays
+ */
+export interface DisplayTrack {
+  id: number;
+  number?: number;
+  title: string;
+  artist?: string;
+  album?: string;
+  albumArt?: string;
+  albumId?: string;
+  artistId?: number;
+  duration: string;
+  durationSeconds: number;
+  hires?: boolean;
+  bitDepth?: number;
+  samplingRate?: number;
+  isrc?: string;
+  isLocal?: boolean;
+  localTrackId?: number;
+  artworkPath?: string;
+}
+
 // ============ Local Library Types ============
 
 export interface LocalLibraryTrack {

src/routes/+page.svelte

@@ -118,16 +118,26 @@
     AlbumDetail,
     ArtistDetail,
     PlaylistTrack,
+    DisplayTrack,
     LocalLibraryTrack,
     SongLinkResponse
   } from '$lib/types';
 
+  // Adapters
+  import {
+    convertQobuzAlbum,
+    convertQobuzArtist,
+    formatDuration
+  } from '$lib/adapters/qobuzAdapters';
+
   // Services
   import {
     playTrack,
     setToastCallback as setPlaybackToastCallback,
     checkTrackFavorite,
     toggleTrackFavorite,
+    showTrackNotification,
+    updateLastfmNowPlaying,
     cleanup as cleanupPlayback
   } from '$lib/services/playbackService';
 
@@ -250,41 +260,6 @@
     }
   }
 
-  function convertQobuzAlbum(album: QobuzAlbum): AlbumDetail {
-    const artwork = album.image?.large || album.image?.thumbnail || album.image?.small || '';
-    const quality = album.hires_streamable && album.maximum_bit_depth && album.maximum_sampling_rate
-      ? `${album.maximum_bit_depth}-Bit / ${album.maximum_sampling_rate} kHz`
-      : 'CD Quality';
-
-    return {
-      id: album.id,
-      artwork,
-      title: album.title,
-      artist: album.artist?.name || 'Unknown Artist',
-      artistId: album.artist?.id,
-      year: album.release_date_original?.split('-')[0] || '',
-      label: album.label?.name || '',
-      genre: album.genre?.name || '',
-      quality,
-      trackCount: album.tracks_count || album.tracks?.items?.length || 0,
-      duration: formatDurationMinutes(album.duration || 0),
-      tracks: album.tracks?.items?.map((track, index) => ({
-        id: track.id,
-        number: index + 1,
-        title: track.title,
-        artist: track.performer?.name,
-        duration: formatDuration(track.duration),
-        durationSeconds: track.duration,
-        quality: track.hires_streamable ? 'Hi-Res' : 'CD',
-        hires: track.hires_streamable,
-        bitDepth: track.maximum_bit_depth,
-        samplingRate: track.maximum_sampling_rate,
-        albumId: album.id,
-        artistId: track.performer?.id ?? album.artist?.id,
-        isrc: track.isrc
-      })) || []
-    };
-  }
 
   async function handleArtistClick(artistId: number) {
     try {
@@ -301,43 +276,6 @@
     }
   }
 
-  function convertQobuzArtist(artist: QobuzArtist): ArtistDetail {
-    const image = artist.image?.large || artist.image?.thumbnail || artist.image?.small;
-
-    return {
-      id: artist.id,
-      name: artist.name,
-      image,
-      albumsCount: artist.albums_count,
-      biography: artist.biography,
-      albums: artist.albums?.items?.map(album => {
-        const artwork = album.image?.large || album.image?.thumbnail || album.image?.small || '';
-        const quality = album.hires_streamable && album.maximum_bit_depth && album.maximum_sampling_rate
-          ? `${album.maximum_bit_depth}bit/${album.maximum_sampling_rate}kHz`
-          : 'CD Quality';
-        return {
-          id: album.id,
-          title: album.title,
-          artwork,
-          year: album.release_date_original?.split('-')[0],
-          quality
-        };
-      }) || [],
-      totalAlbums: artist.albums?.total || artist.albums_count || 0
-    };
-  }
-
-  function formatDuration(seconds: number): string {
-    const mins = Math.floor(seconds / 60);
-    const secs = Math.floor(seconds % 60);
-    return `${mins}:${secs.toString().padStart(2, '0')}`;
-  }
-
-  function formatDurationMinutes(seconds: number): string {
-    const mins = Math.floor(seconds / 60);
-    const secs = Math.floor(seconds % 60);
-    return `${mins}:${secs.toString().padStart(2, '0')}`;
-  }
 
   // Album-specific queue track builder (needs selectedAlbum context)
   function buildAlbumQueueTrack(track: Track): BackendQueueTrack {
@@ -828,14 +766,19 @@
     }
   }
 
-  async function handlePlaylistTrackPlay(track: PlaylistTrack) {
-    console.log('Playing playlist track:', track);
+  /**
+   * Handle playback of DisplayTrack (used by ArtistDetailView, PlaylistDetailView, FavoritesView)
+   * This is fire-and-forget to match view callback signatures
+   */
+  function handleDisplayTrackPlay(track: DisplayTrack): void {
+    console.log('Playing display track:', track);
 
     const quality = track.hires && track.bitDepth && track.samplingRate
       ? `${track.bitDepth}bit/${track.samplingRate}kHz`
       : 'CD Quality';
 
-    await playTrack({
+    // Fire-and-forget async call
+    playTrack({
       id: track.id,
       title: track.title,
       artist: track.artist || 'Unknown Artist',
@@ -1207,7 +1150,7 @@
           artist={selectedArtist}
           onBack={goBack}
           onAlbumClick={handleAlbumClick}
-          onTrackPlay={handlePlaylistTrackPlay}
+          onTrackPlay={handleDisplayTrackPlay}
           onTrackPlayNext={queueQobuzTrackNext}
           onTrackPlayLater={queueQobuzTrackLater}
           onTrackAddFavorite={handleAddToFavorites}
@@ -1228,7 +1171,7 @@
         <PlaylistDetailView
           playlistId={selectedPlaylistId}
           onBack={goBack}
-          onTrackPlay={handlePlaylistTrackPlay}
+          onTrackPlay={handleDisplayTrackPlay}
           onTrackPlayNext={queuePlaylistTrackNext}
           onTrackPlayLater={queuePlaylistTrackLater}
           onTrackAddFavorite={handleAddToFavorites}
@@ -1248,7 +1191,7 @@
       {:else if activeView === 'favorites'}
         <FavoritesView
           onAlbumClick={handleAlbumClick}
-          onTrackPlay={handlePlaylistTrackPlay}
+          onTrackPlay={handleDisplayTrackPlay}
           onArtistClick={handleArtistClick}
           onTrackPlayNext={queuePlaylistTrackNext}
           onTrackPlayLater={queuePlaylistTrackLater}