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/hooks/useMiniWindowSetup.ts

@@ -0,0 +1,52 @@
+import { useEffect } from 'react';
+import { invoke } from '@tauri-apps/api/core';
+import { useAuthStore } from '../store/authStore';
+import { IS_LINUX } from '../utils/platform';
+import {
+  EXPANDED_SIZE, EXPANDED_MIN, readStoredExpandedHeight,
+} from '../utils/miniPlayerHelpers';
+
+/** Three window-bound setup effects bundled together:
+ *  - Linux WebKitGTK smooth-scroll per-window (re-applies after auth hydrates
+ *    so preloaded/hidden mini matches the Settings toggle).
+ *  - Initial expanded-size restore: Rust always builds the window at the
+ *    collapsed size, so on cold start with queueOpen=true we resize once.
+ *  - Always-on-top reapply on mount and on focus: WMs silently drop the
+ *    constraint after Hide/Show cycles, so we re-assert it whenever the user
+ *    actually brings the window to the foreground. */
+export function useMiniWindowSetup(alwaysOnTop: boolean, initialQueueOpen: boolean) {
+  useEffect(() => {
+    if (!IS_LINUX) return;
+    const apply = () => {
+      invoke('set_linux_webkit_smooth_scrolling', {
+        enabled: useAuthStore.getState().linuxWebkitKineticScroll,
+      }).catch(() => {});
+    };
+    apply();
+    return useAuthStore.persist.onFinishHydration(() => {
+      apply();
+    });
+  }, []);
+
+  useEffect(() => {
+    if (!initialQueueOpen) return;
+    invoke('resize_mini_player', {
+      width: EXPANDED_SIZE.w,
+      height: readStoredExpandedHeight(),
+      minWidth: EXPANDED_MIN.w,
+      minHeight: EXPANDED_MIN.h,
+    }).catch(() => {});
+    // eslint-disable-next-line react-hooks/exhaustive-deps
+  }, []);
+
+  useEffect(() => {
+    invoke('set_mini_player_always_on_top', { onTop: alwaysOnTop }).catch(() => {});
+    const reapply = () => {
+      if (alwaysOnTop) {
+        invoke('set_mini_player_always_on_top', { onTop: true }).catch(() => {});
+      }
+    };
+    window.addEventListener('focus', reapply);
+    return () => window.removeEventListener('focus', reapply);
+  }, [alwaysOnTop]);
+}