refactor(mini-player): H6 — split MiniPlayer.tsx 820 → 218 LOC across 11 files (#669)

* refactor(mini-player): H6 — extract helpers + constants

Pure code-move: window-size constants, localStorage keys + read helpers,
toMini track shape, initialSnapshot, and fmt(seconds) → utils/miniPlayerHelpers.ts.

MiniPlayer.tsx: 820 → 745 LOC.

* refactor(mini-player): H6 — extract MiniTitlebar + MiniMeta + MiniControls

Three small visual subcomponents move into components/miniPlayer/.
MiniPlayer drops the now-unused Pin/PinOff/Maximize2/X/Play/Pause/
SkipBack/SkipForward lucide icons and the CachedImage import.

MiniPlayer.tsx: 745 → 665 LOC.

* refactor(mini-player): H6 — extract MiniToolbar + useMiniVolumePopover

The whole toolbar (volume button + portaled popover, shuffle, gapless/
crossfade/infinite, queue toggle) moves into MiniToolbar.tsx. The volume
popover open-state + ref/style positioning + outside-click/Escape close
move into the useMiniVolumePopover hook.

MiniPlayer.tsx: 665 → 492 LOC.

* refactor(mini-player): H6 — extract MiniQueue + useMiniQueueDrag

The OverlayScrollArea + queue.map block moves into MiniQueue.tsx. The
PsyDnD wiring (drop-inside emits mini:reorder, drop-outside emits
mini:remove, reorder math collapsing same-position + adjusting for shift)
moves into the useMiniQueueDrag hook.

MiniPlayer.tsx: 492 → 346 LOC.

* refactor(mini-player): H6 — extract useMiniSync + useMiniWindowSetup + useMiniKeyboardShortcuts

Three more hooks pull the remaining side-effect islands out of MiniPlayer:
  - useMiniSync owns mini:ready emit on mount + focus, plus the
    mini:sync / audio:progress / audio:ended listeners. The hidden-window
    visibility ref that gates progress now lives inside the hook.
  - useMiniWindowSetup bundles three small window-bound effects:
    Linux WebKitGTK smooth-scroll, the cold-start expanded-size restore
    when queueOpen=true, and always-on-top reapply on mount + focus.
  - useMiniKeyboardShortcuts moves the keyboard-shortcut bridge wiring.

MiniPlayer.tsx: 346 → 218 LOC.

src/components/miniPlayer/MiniTitlebar.tsx

@@ -0,0 +1,68 @@
+import { Maximize2, Pin, PinOff, X } from 'lucide-react';
+import type { TFunction } from 'i18next';
+import { IS_LINUX } from '../../utils/platform';
+
+interface Props {
+  trackTitle: string | undefined;
+  alwaysOnTop: boolean;
+  toggleOnTop: () => void;
+  showMain: () => void;
+  closeMini: () => void;
+  t: TFunction;
+}
+
+export function MiniTitlebar({
+  trackTitle, alwaysOnTop, toggleOnTop, showMain, closeMini, t,
+}: Props) {
+  return (
+    <div
+      className={`mini-player__titlebar${!IS_LINUX ? ' mini-player__titlebar--mac' : ''}`}
+      {...(!IS_LINUX ? {} : { 'data-tauri-drag-region': true })}
+    >
+      {IS_LINUX ? (
+        <span className="mini-player__titlebar-title" data-tauri-drag-region>
+          {trackTitle ?? 'Psysonic Mini'}
+        </span>
+      ) : (
+        // macOS/Windows already render a native titlebar with the window
+        // title + close button; we just need a flexible spacer so the
+        // action buttons sit right.
+        <span className="mini-player__titlebar-spacer" />
+      )}
+      <button
+        type="button"
+        className={`mini-player__titlebar-btn${alwaysOnTop ? ' mini-player__titlebar-btn--active' : ''}`}
+        onClick={toggleOnTop}
+        data-tauri-drag-region="false"
+        data-tooltip={alwaysOnTop ? t('miniPlayer.pinOff') : t('miniPlayer.pinOnTop')}
+        aria-label={alwaysOnTop ? t('miniPlayer.pinOff') : t('miniPlayer.pinOnTop')}
+      >
+        {alwaysOnTop ? <Pin size={13} /> : <PinOff size={13} />}
+      </button>
+      <button
+        type="button"
+        className="mini-player__titlebar-btn"
+        onClick={showMain}
+        data-tauri-drag-region="false"
+        data-tooltip={t('miniPlayer.openMainWindow')}
+        aria-label={t('miniPlayer.openMainWindow')}
+      >
+        <Maximize2 size={13} />
+      </button>
+      {/* macOS + Windows already provide Close via the native titlebar —
+          skip the duplicate so the in-app titlebar stays minimal. */}
+      {IS_LINUX && (
+        <button
+          type="button"
+          className="mini-player__titlebar-btn mini-player__titlebar-btn--close"
+          onClick={closeMini}
+          data-tauri-drag-region="false"
+          data-tooltip={t('miniPlayer.close')}
+          aria-label={t('miniPlayer.close')}
+        >
+          <X size={13} />
+        </button>
+      )}
+    </div>
+  );
+}