feat(queue): collapse ReplayGain into a click-to-expand badge

Per @cucadmuh's feedback: the presence of ReplayGain matters more than
the actual numbers. The tech bar now shows a small 'RG' pill on line 1
whenever the track has any RG metadata; hovering reveals the values via
tooltip, clicking persistently expands the second line.

- Source icon stays inline before the format string (was getting
  separated from FLAC by the centred stack layout)
- Pill uses --accent-tinted color-mix so it adapts to every theme
- ChevronDown rotates on expand for a clear affordance
- New persisted state: themeStore.expandReplayGain (default collapsed)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/components/QueuePanel.tsx

@@ -1,6 +1,6 @@
 import React, { useState, useRef, useMemo } from 'react';
 import { Track, usePlayerStore, songToTrack } from '../store/playerStore';
-import { Play, Music, Star, X, Trash2, Save, FolderOpen, Shuffle, Infinity, Waves, MicVocal, ListMusic, Check, ListPlus, ArrowUpToLine, Radio, HardDrive } from 'lucide-react';
+import { Play, Music, Star, X, Trash2, Save, FolderOpen, Shuffle, Infinity, Waves, MicVocal, ListMusic, Check, ListPlus, ArrowUpToLine, Radio, HardDrive, ChevronDown } from 'lucide-react';
 import { buildCoverArtUrl, coverArtCacheKey, getAlbum, getPlaylists, getPlaylist, updatePlaylist, deletePlaylist, SubsonicPlaylist } from '../api/subsonic';
 import { usePlaylistStore } from '../store/playlistStore';
 import { useCachedUrl } from './CachedImage';
@@ -8,6 +8,7 @@ import { useEffect } from 'react';
 import { useTranslation } from 'react-i18next';
 import { useNavigate } from 'react-router-dom';
 import { useAuthStore } from '../store/authStore';
+import { useThemeStore } from '../store/themeStore';
 import { useLyricsStore } from '../store/lyricsStore';
 import { useDragDrop } from '../contexts/DragDropContext';
 import LyricsPane from './LyricsPane';
@@ -267,6 +268,8 @@ export default function QueuePanel() {
 
   const [showRemainingTime, setShowRemainingTime] = useState(false);
   const [showCrossfadePopover, setShowCrossfadePopover] = useState(false);
+  const expandReplayGain = useThemeStore(s => s.expandReplayGain);
+  const setExpandReplayGain = useThemeStore(s => s.setExpandReplayGain);
   const crossfadeBtnRef = useRef<HTMLButtonElement>(null);
   const crossfadePopoverRef = useRef<HTMLDivElement>(null);
 
@@ -454,28 +457,44 @@ export default function QueuePanel() {
             const baseLine = baseParts.join(' · ');
             const rgLine = rgParts.join(' · ');
             if (!baseLine && !rgLine && !playbackSource) return null;
+            const showRgLine = expandReplayGain && !!rgLine;
             return (
-              <div className={`queue-current-tech${rgLine ? ' queue-current-tech--two-line' : ''}`}>
-                {playbackSource && (
-                  <span
-                    className="queue-current-tech-source"
-                    data-tooltip={
-                      playbackSource === 'offline'
-                        ? t('queue.sourceOffline')
-                        : playbackSource === 'hot'
-                          ? t('queue.sourceHot')
-                          : t('queue.sourceStream')
-                    }
-                    aria-hidden
-                  >
-                    {playbackSource === 'offline' && <FolderOpen size={11} strokeWidth={2.25} />}
-                    {playbackSource === 'hot' && <HardDrive size={11} strokeWidth={2.25} />}
-                    {playbackSource === 'stream' && <Waves size={11} strokeWidth={2.25} />}
-                  </span>
-                )}
+              <div className={`queue-current-tech${showRgLine ? ' queue-current-tech--two-line' : ''}`}>
                 <div className="queue-current-tech-stack">
-                  {baseLine && <span className="queue-current-tech-main">{baseLine}</span>}
-                  {rgLine && (
+                  <div className="queue-current-tech-row">
+                    {playbackSource && (
+                      <span
+                        className="queue-current-tech-source"
+                        data-tooltip={
+                          playbackSource === 'offline'
+                            ? t('queue.sourceOffline')
+                            : playbackSource === 'hot'
+                              ? t('queue.sourceHot')
+                              : t('queue.sourceStream')
+                        }
+                        aria-hidden
+                      >
+                        {playbackSource === 'offline' && <FolderOpen size={11} strokeWidth={2.25} />}
+                        {playbackSource === 'hot' && <HardDrive size={11} strokeWidth={2.25} />}
+                        {playbackSource === 'stream' && <Waves size={11} strokeWidth={2.25} />}
+                      </span>
+                    )}
+                    {baseLine && <span className="queue-current-tech-main">{baseLine}</span>}
+                    {rgLine && (
+                      <button
+                        type="button"
+                        className={`queue-current-tech-rg-badge${showRgLine ? ' queue-current-tech-rg-badge--open' : ''}`}
+                        data-tooltip={`${t('queue.replayGain')} · ${rgLine}`}
+                        aria-expanded={showRgLine}
+                        aria-label={t('queue.replayGain')}
+                        onClick={() => setExpandReplayGain(!expandReplayGain)}
+                      >
+                        RG
+                        <ChevronDown size={9} strokeWidth={2.5} />
+                      </button>
+                    )}
+                  </div>
+                  {showRgLine && (
                     <span className="queue-current-tech-rg">
                       <span className="queue-current-tech-rg-label">{t('queue.replayGain')}</span>
                       {' · '}{rgLine}

src/store/themeStore.ts

@@ -24,6 +24,8 @@ interface ThemeState {
   setShowBitrate: (v: boolean) => void;
   showRemainingTime: boolean;
   setShowRemainingTime: (v: boolean) => void;
+  expandReplayGain: boolean;
+  setExpandReplayGain: (v: boolean) => void;
 }
 
 export function getScheduledTheme(state: Pick<ThemeState, 'enableThemeScheduler' | 'theme' | 'themeDay' | 'themeNight' | 'timeDayStart' | 'timeNightStart'>): string {
@@ -63,6 +65,8 @@ export const useThemeStore = create<ThemeState>()(
       setShowBitrate: (v) => set({ showBitrate: v }),
       showRemainingTime: false,
       setShowRemainingTime: (v) => set({ showRemainingTime: v }),
+      expandReplayGain: false,
+      setExpandReplayGain: (v) => set({ expandReplayGain: v }),
     }),
     {
       name: 'psysonic_theme',

src/styles/layout.css

@@ -1725,9 +1725,10 @@
   text-overflow: ellipsis;
 }
 
-/* Two-line layout: base info on top, ReplayGain underneath. The stack
-   wraps both spans so the source icon stays vertically centered next to
-   the whole text block. */
+/* Two-line layout: base info + RG badge on top, optional ReplayGain
+   values underneath when the badge is expanded. The stack wraps both
+   rows so the source icon stays vertically centered next to the whole
+   text block. */
 .queue-current-tech-stack {
   min-width: 0;
   display: flex;
@@ -1736,6 +1737,44 @@
   gap: 1px;
 }
 
+.queue-current-tech-row {
+  min-width: 0;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  gap: 6px;
+}
+
+/* Pill-shaped toggle that signals "this track has ReplayGain metadata"
+   without committing screen space to the numbers — values appear in the
+   tooltip and on the second line when expanded. */
+.queue-current-tech-rg-badge {
+  flex-shrink: 0;
+  display: inline-flex;
+  align-items: center;
+  gap: 2px;
+  padding: 1px 5px 1px 6px;
+  border: 1px solid color-mix(in srgb, var(--accent) 35%, transparent);
+  background: color-mix(in srgb, var(--accent) 12%, transparent);
+  color: var(--accent);
+  border-radius: 999px;
+  font: inherit;
+  font-size: 8px;
+  letter-spacing: 0.06em;
+  cursor: pointer;
+  transition: background 0.12s, border-color 0.12s, transform 0.12s;
+}
+.queue-current-tech-rg-badge:hover {
+  background: color-mix(in srgb, var(--accent) 22%, transparent);
+  border-color: color-mix(in srgb, var(--accent) 55%, transparent);
+}
+.queue-current-tech-rg-badge svg {
+  transition: transform 0.18s ease;
+}
+.queue-current-tech-rg-badge--open svg {
+  transform: rotate(180deg);
+}
+
 .queue-current-tech-rg {
   min-width: 0;
   max-width: 100%;