feat(flutter): cosmetic reveal animations (Slice F)

Final slice of the per-item rendering pass. Wraps every tile widget
in an AnimatedSwitcher between the skeleton placeholder and the real
card. 220ms cross-fade with easeOut: tiles "settle into place"
rather than hard-cutting from shimmer to content. Since each tile
fades independently as its data lands — and the HydrationQueue's
concurrency cap drains in a natural cascade — the overall feel is
the staged "page builds piece by piece" effect we wanted, with no
per-tile position math required.

Bumps CachedNetworkImage fadeInDuration from zero to 120ms (server_
image.dart, discover_screen.dart). Imperceptible on cache hits since
the image decodes synchronously; on cache misses the bytes fade in
smoothly instead of popping. Slice 1's "zero fade" call was right
about the 500ms default being a regression, but 120ms threads the
needle.

Playlist detail wraps its body in the same AnimatedSwitcher so the
cold-load skeleton page cross-fades into the real track list.

Tiles affected: home _AlbumTile / _ArtistTile / _TrackTile + liked
_LikedAlbumTile / _LikedArtistTile / _LikedTrackRow + playlist
_SkeletonBody / _Body. All keyed via ValueKey so AnimatedSwitcher
detects the transition.

End of the per-item pass. Net behavior: cold visits paint shaped
pages instantly with skeletons, content cascades in as hydration
lands; warm visits paint fully from drift in the first frame.

flutter_client/lib/discover/discover_screen.dart

@@ -208,7 +208,7 @@ class _ResultTile extends StatelessWidget {
                 : CachedNetworkImage(
                     imageUrl: row.imageUrl,
                     fit: BoxFit.cover,
-                    fadeInDuration: Duration.zero,
+                    fadeInDuration: const Duration(milliseconds: 120),
                     fadeOutDuration: Duration.zero,
                     errorWidget: (_, __, ___) =>
                         Icon(Icons.album, color: fs.ash),

flutter_client/lib/library/home_screen.dart

@@ -83,6 +83,13 @@ class HomeScreen extends ConsumerWidget {
 
 // ─── Per-tile widgets ────────────────────────────────────────────────
 
+/// Duration of the skeleton→content cross-fade. 220ms reads as "tile
+/// settled into place" — longer drags, shorter feels like a hard cut.
+/// Each tile cross-fades independently when its data lands, so the
+/// natural cascade from the hydration queue's bounded concurrency
+/// produces a staged-reveal feel without any per-tile delay math.
+const Duration _tileRevealDuration = Duration(milliseconds: 220);
+
 /// Album tile: skeleton until albumTileProvider yields a populated row.
 class _AlbumTile extends ConsumerWidget {
   const _AlbumTile({required this.id});
@@ -92,10 +99,17 @@ class _AlbumTile extends ConsumerWidget {
   Widget build(BuildContext context, WidgetRef ref) {
     final asyncAlbum = ref.watch(albumTileProvider(id));
     final album = asyncAlbum.asData?.value;
-    if (album == null) return const SkeletonAlbumTile();
-    return AlbumCard(
-      album: album,
-      onTap: () => context.push('/albums/${album.id}', extra: album),
+    return AnimatedSwitcher(
+      duration: _tileRevealDuration,
+      switchInCurve: Curves.easeOut,
+      child: album == null
+          ? const SkeletonAlbumTile(key: ValueKey('skeleton'))
+          : AlbumCard(
+              key: ValueKey('album-${album.id}'),
+              album: album,
+              onTap: () =>
+                  context.push('/albums/${album.id}', extra: album),
+            ),
     );
   }
 }
@@ -109,10 +123,17 @@ class _ArtistTile extends ConsumerWidget {
   Widget build(BuildContext context, WidgetRef ref) {
     final asyncArtist = ref.watch(artistTileProvider(id));
     final artist = asyncArtist.asData?.value;
-    if (artist == null) return const SkeletonArtistTile();
-    return ArtistCard(
-      artist: artist,
-      onTap: () => context.push('/artists/${artist.id}', extra: artist),
+    return AnimatedSwitcher(
+      duration: _tileRevealDuration,
+      switchInCurve: Curves.easeOut,
+      child: artist == null
+          ? const SkeletonArtistTile(key: ValueKey('skeleton'))
+          : ArtistCard(
+              key: ValueKey('artist-${artist.id}'),
+              artist: artist,
+              onTap: () =>
+                  context.push('/artists/${artist.id}', extra: artist),
+            ),
     );
   }
 }
@@ -131,15 +152,18 @@ class _TrackTile extends ConsumerWidget {
   Widget build(BuildContext context, WidgetRef ref) {
     final asyncTrack = ref.watch(trackTileProvider(id));
     final track = asyncTrack.asData?.value;
-    if (track == null) {
-      // Compact-track placeholder: same 56dp footprint as the real card
-      // so the row's intrinsic width doesn't change as tiles hydrate.
-      return const _CompactTrackSkeleton();
-    }
-    return CompactTrackCard(
-      track: track,
-      sectionTracks: _resolveSectionTracks(ref, sectionIds),
-      index: sectionIds.indexOf(id).clamp(0, sectionIds.length - 1),
+    return AnimatedSwitcher(
+      duration: _tileRevealDuration,
+      switchInCurve: Curves.easeOut,
+      child: track == null
+          ? const _CompactTrackSkeleton(key: ValueKey('skeleton'))
+          : CompactTrackCard(
+              key: ValueKey('track-${track.id}'),
+              track: track,
+              sectionTracks: _resolveSectionTracks(ref, sectionIds),
+              index:
+                  sectionIds.indexOf(id).clamp(0, sectionIds.length - 1),
+            ),
     );
   }
 
@@ -161,7 +185,7 @@ class _TrackTile extends ConsumerWidget {
 /// CompactTrackCard so swapping in the real card doesn't shift the
 /// row's height.
 class _CompactTrackSkeleton extends StatelessWidget {
-  const _CompactTrackSkeleton();
+  const _CompactTrackSkeleton({super.key});
   @override
   Widget build(BuildContext context) {
     final fs = Theme.of(context).extension<FabledSwordTheme>()!;

flutter_client/lib/library/library_screen.dart

@@ -631,6 +631,11 @@ class _LikedTab extends ConsumerWidget {
   }
 }
 
+/// Skeleton→content cross-fade duration. Matches home_screen so the
+/// reveal feel is consistent across surfaces. See _tileRevealDuration
+/// in home_screen.dart for the rationale.
+const Duration _likedTileReveal = Duration(milliseconds: 220);
+
 /// Liked-Artists carousel tile. Skeleton until artistTileProvider
 /// yields a populated row.
 class _LikedArtistTile extends ConsumerWidget {
@@ -640,10 +645,17 @@ class _LikedArtistTile extends ConsumerWidget {
   @override
   Widget build(BuildContext context, WidgetRef ref) {
     final artist = ref.watch(artistTileProvider(id)).asData?.value;
-    if (artist == null) return const SkeletonArtistTile();
-    return ArtistCard(
-      artist: artist,
-      onTap: () => context.push('/artists/${artist.id}', extra: artist),
+    return AnimatedSwitcher(
+      duration: _likedTileReveal,
+      switchInCurve: Curves.easeOut,
+      child: artist == null
+          ? const SkeletonArtistTile(key: ValueKey('skeleton'))
+          : ArtistCard(
+              key: ValueKey('artist-${artist.id}'),
+              artist: artist,
+              onTap: () =>
+                  context.push('/artists/${artist.id}', extra: artist),
+            ),
     );
   }
 }
@@ -657,10 +669,16 @@ class _LikedAlbumTile extends ConsumerWidget {
   @override
   Widget build(BuildContext context, WidgetRef ref) {
     final album = ref.watch(albumTileProvider(id)).asData?.value;
-    if (album == null) return const SkeletonAlbumTile();
-    return AlbumCard(
-      album: album,
-      onTap: () => context.push('/albums/${album.id}', extra: album),
+    return AnimatedSwitcher(
+      duration: _likedTileReveal,
+      switchInCurve: Curves.easeOut,
+      child: album == null
+          ? const SkeletonAlbumTile(key: ValueKey('skeleton'))
+          : AlbumCard(
+              key: ValueKey('album-${album.id}'),
+              album: album,
+              onTap: () => context.push('/albums/${album.id}', extra: album),
+            ),
     );
   }
 }
@@ -677,21 +695,27 @@ class _LikedTrackRow extends ConsumerWidget {
   @override
   Widget build(BuildContext context, WidgetRef ref) {
     final track = ref.watch(trackTileProvider(id)).asData?.value;
-    if (track == null) return const SkeletonTrackRow();
-    return TrackRow(
-      track: track,
-      onTap: () {
-        final hydrated = <TrackRef>[];
-        for (final i in sectionIds) {
-          final v = ref.read(trackTileProvider(i)).asData?.value;
-          if (v != null) hydrated.add(v);
-        }
-        final start = hydrated.indexWhere((t) => t.id == id);
-        ref.read(playerActionsProvider).playTracks(
-              hydrated,
-              initialIndex: start < 0 ? 0 : start,
-            );
-      },
+    return AnimatedSwitcher(
+      duration: _likedTileReveal,
+      switchInCurve: Curves.easeOut,
+      child: track == null
+          ? const SkeletonTrackRow(key: ValueKey('skeleton'))
+          : TrackRow(
+              key: ValueKey('track-${track.id}'),
+              track: track,
+              onTap: () {
+                final hydrated = <TrackRef>[];
+                for (final i in sectionIds) {
+                  final v = ref.read(trackTileProvider(i)).asData?.value;
+                  if (v != null) hydrated.add(v);
+                }
+                final start = hydrated.indexWhere((t) => t.id == id);
+                ref.read(playerActionsProvider).playTracks(
+                      hydrated,
+                      initialIndex: start < 0 ? 0 : start,
+                    );
+              },
+            ),
     );
   }
 }

flutter_client/lib/playlists/playlist_detail_screen.dart

@@ -67,16 +67,23 @@ class PlaylistDetailScreen extends ConsumerWidget {
                 overflow: TextOverflow.ellipsis,
               ),
       ),
-      body: detail.when(
-        // Loading from a seed: render the header immediately + the
-        // exact track-count of skeleton rows, instead of an opaque
-        // full-screen spinner. Cold-visit feel: shaped page with
-        // shimmering rows that swap in for real ones as the bulk
-        // detail fetch lands.
-        loading: () => _SkeletonBody(seed: seed),
-        error: (e, _) =>
-            Center(child: Text('$e', style: TextStyle(color: fs.error))),
-        data: (d) => _Body(detail: d),
+      // AnimatedSwitcher between the skeleton body and the real body
+      // smooths the cold-visit moment when bulk detail lands. 220ms
+      // matches the per-tile reveal feel used on home / liked tabs.
+      body: AnimatedSwitcher(
+        duration: const Duration(milliseconds: 220),
+        switchInCurve: Curves.easeOut,
+        child: detail.when(
+          loading: () => _SkeletonBody(
+            key: const ValueKey('skeleton'),
+            seed: seed,
+          ),
+          error: (e, _) => Center(
+            key: const ValueKey('error'),
+            child: Text('$e', style: TextStyle(color: fs.error)),
+          ),
+          data: (d) => _Body(key: const ValueKey('body'), detail: d),
+        ),
       ),
     );
   }
@@ -88,7 +95,7 @@ class PlaylistDetailScreen extends ConsumerWidget {
 /// (deep link straight to a playlist with no prior cache) the
 /// skeleton renders a small default and grows when real data arrives.
 class _SkeletonBody extends StatelessWidget {
-  const _SkeletonBody({this.seed});
+  const _SkeletonBody({super.key, this.seed});
   final Playlist? seed;
 
   static const _defaultSkeletonCount = 8;
@@ -163,7 +170,7 @@ class _PlaylistTrackSkeleton extends StatelessWidget {
 }
 
 class _Body extends ConsumerWidget {
-  const _Body({required this.detail});
+  const _Body({super.key, required this.detail});
   final PlaylistDetail detail;
 
   @override

flutter_client/lib/shared/widgets/server_image.dart

@@ -61,10 +61,12 @@ class ServerImage extends ConsumerWidget {
           imageUrl: resolved,
           httpHeaders: headers,
           fit: fit,
-          // No fadeIn — covers paint instantly once cached, and the
-          // default 500ms fade looks like a regression on a populated
-          // grid.
-          fadeInDuration: Duration.zero,
+          // 120ms feels like cover bytes settling in on a cache miss
+          // (smoother than the abrupt zero-fade); on cache hits the
+          // image is decoded synchronously so the fade is imperceptible.
+          // The default 500ms is too long — looks like a regression on
+          // a populated grid.
+          fadeInDuration: const Duration(milliseconds: 120),
           fadeOutDuration: Duration.zero,
           // Keep failures local — a single 401/timeout shouldn't dump
           // a stack trace or replace the parent Container's background.