refactor(artists): I.4 — split Artists.tsx 520 → 233 LOC across 6 files (#676)

* refactor(artists): extract helpers + constants

Pull ALL_SENTINEL / ALPHABET / ARTIST_LIST_* row-height estimates,
the ArtistListFlatRow union, CTP_COLORS palette, and the deterministic
nameColor / nameInitial helpers into utils/artistsHelpers.ts.

Artists.tsx: 520 → 496 LOC.

* refactor(artists): extract ArtistAvatars subcomponents

Pull ArtistCardAvatar (300px, grid view) and ArtistRowAvatar (64px, list
view) into components/artists/ArtistAvatars.tsx. Both fall back to a
hashed-Catppuccin monogram when artist images are off or no cover art
is available.

Artists.tsx: 496 → 436 LOC.

* refactor(artists): extract useArtistsFiltering hook

Bundle the letter/text/star filter pipeline, visible-slice memo,
group-by-letter, and the virtualizer flat-rows list into
hooks/useArtistsFiltering.ts. List-view-only outputs short-circuit when
grid view is active.

Artists.tsx: 436 → 386 LOC.

* refactor(artists): extract useArtistsInfiniteScroll hook

Bundle visibleCount + loadingMore state, the sentinel
IntersectionObserver, loadMore callback, and the filter-change reset
into hooks/useArtistsInfiniteScroll.ts. The observer no longer takes
hasMore — the sentinel element only mounts while there is more data,
so the observer attaches/detaches naturally with it.

Artists.tsx: 386 → 370 LOC.

* refactor(artists): extract ArtistsGridView + ArtistsListView

Move the grid card layout to components/artists/ArtistsGridView.tsx and
the dual-path list layout (non-virtualized fallback + virtualized stream)
to components/artists/ArtistsListView.tsx. Both paths now share an
internal ArtistListRow component so click + context-menu behaviour is
identical regardless of which renderer is active.

Artists.tsx: 370 → 233 LOC.

src/components/artists/ArtistsListView.tsx

@@ -0,0 +1,183 @@
+import React from 'react';
+import type { NavigateFunction } from 'react-router-dom';
+import type { Virtualizer } from '@tanstack/react-virtual';
+import type { TFunction } from 'i18next';
+import type { SubsonicArtist } from '../../api/subsonicTypes';
+import type { PlayerState } from '../../store/playerStoreTypes';
+import type { ArtistListFlatRow } from '../../utils/artistsHelpers';
+import { ArtistRowAvatar } from './ArtistAvatars';
+
+interface RowProps {
+  artist: SubsonicArtist;
+  selectionMode: boolean;
+  selectedIds: Set<string>;
+  selectedArtists: SubsonicArtist[];
+  showArtistImages: boolean;
+  toggleSelect: (id: string) => void;
+  navigate: NavigateFunction;
+  openContextMenu: PlayerState['openContextMenu'];
+  t: TFunction;
+}
+
+function ArtistListRow({
+  artist,
+  selectionMode,
+  selectedIds,
+  selectedArtists,
+  showArtistImages,
+  toggleSelect,
+  navigate,
+  openContextMenu,
+  t,
+}: RowProps) {
+  return (
+    <button
+      type="button"
+      className={`artist-row${selectionMode && selectedIds.has(artist.id) ? ' selected' : ''}`}
+      onClick={() => {
+        if (selectionMode) {
+          toggleSelect(artist.id);
+        } else {
+          navigate(`/artist/${artist.id}`);
+        }
+      }}
+      onContextMenu={(e) => {
+        e.preventDefault();
+        if (selectionMode && selectedIds.size > 0) {
+          openContextMenu(e.clientX, e.clientY, selectedArtists, 'multi-artist');
+        } else {
+          openContextMenu(e.clientX, e.clientY, artist, 'artist');
+        }
+      }}
+      id={`artist-${artist.id}`}
+      style={selectionMode && selectedIds.has(artist.id) ? {
+        background: 'var(--accent-dim)',
+        color: 'var(--accent)',
+      } : {}}
+    >
+      <ArtistRowAvatar artist={artist} showImages={showArtistImages} />
+      <div style={{ textAlign: 'left' }}>
+        <div className="artist-name">{artist.name}</div>
+        {artist.albumCount != null && (
+          <div className="artist-meta">{t('artists.albumCount', { count: artist.albumCount })}</div>
+        )}
+      </div>
+    </button>
+  );
+}
+
+interface Props {
+  virtualized: boolean;
+  groups: Record<string, SubsonicArtist[]>;
+  letters: string[];
+  artistListFlatRows: ArtistListFlatRow[];
+  artistListVirtualizer: Virtualizer<HTMLElement, Element>;
+  selectionMode: boolean;
+  selectedIds: Set<string>;
+  selectedArtists: SubsonicArtist[];
+  showArtistImages: boolean;
+  toggleSelect: (id: string) => void;
+  navigate: NavigateFunction;
+  openContextMenu: PlayerState['openContextMenu'];
+  t: TFunction;
+}
+
+/**
+ * List view for the artists page. Two render paths:
+ *  - Non-virtualized — emits one `<div class="artist-list">` per starting
+ *    letter, used when the `disableMainstageVirtualLists` perf flag is on
+ *    (mostly for low-end devices where translate-Y positioning costs more
+ *    than the saved DOM nodes).
+ *  - Virtualized — flat `letter / artist / artist / …` row stream sitting
+ *    on a single absolutely-positioned `<div>` whose height matches the
+ *    virtualizer's totalSize.
+ *
+ * Both paths share `ArtistListRow` so click + context-menu behaviour is
+ * identical regardless of the rendering path.
+ */
+export function ArtistsListView({
+  virtualized,
+  groups,
+  letters,
+  artistListFlatRows,
+  artistListVirtualizer,
+  selectionMode,
+  selectedIds,
+  selectedArtists,
+  showArtistImages,
+  toggleSelect,
+  navigate,
+  openContextMenu,
+  t,
+}: Props) {
+  const rowCommonProps = {
+    selectionMode, selectedIds, selectedArtists, showArtistImages,
+    toggleSelect, navigate, openContextMenu, t,
+  };
+
+  if (!virtualized) {
+    return (
+      <>
+        {letters.map(letter => (
+          <div key={letter} style={{ marginBottom: '1.5rem' }}>
+            <h3 className="letter-heading">{letter}</h3>
+            <div className="artist-list">
+              {groups[letter].map(artist => (
+                <ArtistListRow key={artist.id} artist={artist} {...rowCommonProps} />
+              ))}
+            </div>
+          </div>
+        ))}
+      </>
+    );
+  }
+
+  return (
+    <div style={{ position: 'relative', width: '100%' }}>
+      <div
+        style={{
+          height: artistListFlatRows.length === 0 ? 0 : artistListVirtualizer.getTotalSize(),
+          width: '100%',
+          position: 'relative',
+        }}
+      >
+        {artistListVirtualizer.getVirtualItems().map(vi => {
+          const row = artistListFlatRows[vi.index];
+          if (!row) return null;
+          if (row.kind === 'letter') {
+            return (
+              <div
+                key={vi.key}
+                style={{
+                  position: 'absolute',
+                  top: 0,
+                  left: 0,
+                  width: '100%',
+                  transform: `translateY(${vi.start}px)`,
+                }}
+              >
+                <h3 className="letter-heading">{row.letter}</h3>
+              </div>
+            );
+          }
+          const artist = row.artist;
+          return (
+            <div
+              key={vi.key}
+              style={{
+                position: 'absolute',
+                top: 0,
+                left: 0,
+                width: '100%',
+                transform: `translateY(${vi.start}px)`,
+                paddingBottom: row.isLastInLetter ? '1.5rem' : undefined,
+              }}
+            >
+              <ArtistListRow artist={artist} {...rowCommonProps} />
+            </div>
+          );
+        })}
+      </div>
+    </div>
+  );
+}