refactor(player): E.28 — extract storage + hotkey helpers cluster (#592)

Two small file-private bits move out of playerStore.ts:

  - `src/store/queueVisibilityStorage.ts` — `readInitialQueueVisibility`
    and `persistQueueVisibility` (the QueuePanel show/hide toggle
    survives reloads via a localStorage round-trip; SSR / private-mode
    failures swallowed silently).
  - `src/store/queueUndoHotkey.ts` — `installQueueUndoHotkey` (Ctrl+Z /
    Cmd+Z queue undo, Ctrl+Shift+Z redo, document-capture; skips text
    fields so native text undo stays; idempotent via window-scoped
    flag; mini-player window skipped). Added a `_resetQueueUndoHotkeyForTest`
    that removes the keydown listener too (needed so vitest specs
    don't accumulate handlers across tests).

playerStore re-exports `installQueueUndoHotkey` so bootstrap + tests
keep their existing `from './playerStore'` imports. The
queue-visibility helpers were file-private; no re-exports.

Side-cleanup: `getWindowKind` import is gone from playerStore (only
the moved hotkey installer used it).

16 focused tests pin the storage round-trip, the idempotency flag, the
modifier + key matching, the editable-target skip, and the
preventDefault contract.

playerStore 1940 → 1879 LOC.

src/store/queueVisibilityStorage.ts

@@ -0,0 +1,32 @@
+/**
+ * Persists the QueuePanel visibility toggle to localStorage so it
+ * survives reloads. Defaults to true on the first run (no stored value)
+ * and on SSR / non-DOM contexts (`typeof window === 'undefined'`).
+ *
+ * Storage failures (quota, private-mode) are silently ignored — the UI
+ * keeps the in-memory state and the user just loses the persisted
+ * preference after the next restart.
+ */
+
+const QUEUE_VISIBILITY_STORAGE_KEY = 'psysonic_queue_visible';
+
+export function readInitialQueueVisibility(): boolean {
+  if (typeof window === 'undefined') return true;
+  try {
+    const raw = window.localStorage.getItem(QUEUE_VISIBILITY_STORAGE_KEY);
+    if (raw === 'true') return true;
+    if (raw === 'false') return false;
+  } catch {
+    // ignore storage access failures and fall back to default
+  }
+  return true;
+}
+
+export function persistQueueVisibility(visible: boolean): void {
+  if (typeof window === 'undefined') return;
+  try {
+    window.localStorage.setItem(QUEUE_VISIBILITY_STORAGE_KEY, String(visible));
+  } catch {
+    // ignore storage access failures
+  }
+}