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/playlist-details/playlist-details.ts

@@ -85,7 +85,9 @@ import {
     ICON_PLAYLIST,
     ICON_QUEUE,
     ICON_REMOVE,
+    ICON_SHUFFLE,
 } from '@utils/icon-language';
+import { playAll } from '@utils/play-all';
 
 /** One playlist row: the track and its position in the *playlist*,
  *  which is not its position in the filtered view. */
@@ -355,14 +357,32 @@ export class PlaylistDetails
     // Track interactions
     // =================================================================
 
-    private handlePlayAll() {
-        const filePaths = this.tracks
+    private playableFilePaths(): string[] {
+        return this.tracks
             .filter((t) => !t.Phantom)
             .map((t) => t.FilePath);
+    }
 
-        if (filePaths.length === 0) return;
+    private handlePlayAll() {
+        // Start at the first row, not at a random one: the old `true`
+        // was `shuffleStart`, which only picks a random first track
+        // when shuffle mode is already on — so "Play All" quietly did
+        // "play from the top" while leaving the mode as it was.  The
+        // mode semantics now live in `playAll`, shared with the other
+        // track lists.
+        playAll(
+            this.playableFilePaths(),
+            { type: 'playlist', id: this.playlistId, label: this.playlistName },
+            false,
+        );
+    }
 
-        queueStore.setQueue(filePaths, 0, true, { type: 'playlist', id: this.playlistId, label: this.playlistName });
+    private handleShuffleAll() {
+        playAll(
+            this.playableFilePaths(),
+            { type: 'playlist', id: this.playlistId, label: this.playlistName },
+            true,
+        );
     }
 
     private handleTrackClick(
@@ -1599,9 +1619,16 @@ export class PlaylistDetails
                     class="play-all-button"
                     @click=${() => this.handlePlayAll()}
                 >
-                    <wa-icon name="play"></wa-icon>
+                    <wa-icon name=${ICON_PLAY}></wa-icon>
                     Play All
                 </button>
+                <button
+                    class="play-all-button"
+                    @click=${() => this.handleShuffleAll()}
+                >
+                    <wa-icon name=${ICON_SHUFFLE}></wa-icon>
+                    Shuffle All
+                </button>
             </div>
             <div class="track-header">
                 <div class="header-cell col-number">#</div>