feat(library): play all and shuffle all on every track list

Four pages that list tracks — Tracks, genre, artist, and both playlist
views — had no way to start the whole list, or had a broken one. One
shared helper (utils/play-all.ts) now owns what "shuffle this
collection" means: SetQueue's shuffleStart only picks a random first
track when shuffle mode is already on, it does not turn it on, so the
mode is toggled before the queue is set. Each host passes an honest
queue Source (#14): anything that builds a queue names what it built it
from, so "Playing from" stops lying.

Two behaviour changes ride along, both flagged: smart-playlist-details'
Shuffle was a live no-op (shuffleStart without enabling mode played
track 1 in order) and is fixed; playlist-details' Play all drops its
shuffleStart:true, so with shuffle mode already on it now starts at the
first row instead of a random one — the album page's existing
semantics.

Verified: make ui-test (1147, incl. a case that fails when the
smart-playlist fix is reverted), npx tsc --noEmit, make e2e (255,
incl. new play-all and header-fit specs), make lint, make test,
make bindings-check, make css-check; artist header read from
screenshots at 424/320/900 (the pair wraps below the name on a phone).

Closes #31

frontend/src/components/track-list/track-list.ts

@@ -26,7 +26,10 @@ import type { ContextMenuHost, MenuTarget } from '@utils/context-menu-controller
 import { PlayerController } from '@store/controllers/player-controller';
 import { SearchController } from '@store/controllers/search-controller';
 import '@components/page-header/page-header';
-import type { SortOption } from '@components/page-header/page-header';
+import type {
+    SortOption,
+    PageAction,
+} from '@components/page-header/page-header';
 import { TrackListController } from '@store/controllers/tracklist-controller';
 import { FavoritesController } from '@store/controllers/favorites-controller';
 import { queueStore } from '@store/queue-store';
@@ -87,7 +90,9 @@ import {
     ICON_PLAYLIST,
     ICON_PLAY_NEXT,
     ICON_QUEUE,
+    ICON_SHUFFLE,
 } from '@utils/icon-language';
+import { playAll } from '@utils/play-all';
 
 const COLUMN_STORAGE_KEY = 'track-list-column-widths';
 const SORT_FIELD_KEY = 'track-list-sort-field';
@@ -2393,6 +2398,27 @@ export class TrackList
                 .map((c) => ({ id: c.id, label: c.label })),
         ];
 
+        const hasTracks = this.cachedSortedTracks.length > 0;
+
+        const actions: PageAction[] = [
+            {
+                id: 'play-all',
+                label: 'Play all',
+                icon: ICON_PLAY,
+                priority: 1,
+                disabled: !hasTracks,
+                onSelect: this.handlePlayAll,
+            },
+            {
+                id: 'shuffle-all',
+                label: 'Shuffle all',
+                icon: ICON_SHUFFLE,
+                priority: 0,
+                disabled: !hasTracks,
+                onSelect: this.handleShuffleAll,
+            },
+        ];
+
         return html`
             <page-header
                 heading=${this.externalTracks === undefined ? 'Tracks' : ''}
@@ -2404,11 +2430,29 @@ export class TrackList
                 sort-field=${this.sortField ?? ''}
                 sort-direction=${this.sortDirection}
                 search-term=${this.searchCtrl.term}
+                .actions=${actions}
                 @sort-change=${this.onPageHeaderSort}
             ></page-header>
         `;
     }
 
+    /** The queue is the list as displayed, in the order the user sees. */
+    private handlePlayAll = (): void => {
+        playAll(
+            this.cachedSortedTracks.map((t) => t.FilePath),
+            this.effectiveQueueSource,
+            false,
+        );
+    };
+
+    private handleShuffleAll = (): void => {
+        playAll(
+            this.cachedSortedTracks.map((t) => t.FilePath),
+            this.effectiveQueueSource,
+            true,
+        );
+    };
+
     private onPageHeaderSort = (
         e: CustomEvent<{ field: string; direction: 'asc' | 'desc' }>,
     ) => {