fix(shortcuts): use CommandOrControl+N for notification history toggle

- Replaces Ctrl+N default with CommandOrControl+N so the binding works on macOS (Cmd+N) and Windows/Linux (Ctrl+N)
- Updates config example, docs, changelog, and default config to match
- Adds !important to notification stack z-index to prevent stacking-context overrides

src/config/config.test.ts

@@ -98,6 +98,7 @@ test('loads defaults when config is missing', () => {
   assert.equal(config.shortcuts.markAudioCard, 'CommandOrControl+Shift+A');
   assert.equal(config.shortcuts.openCharacterDictionaryManager, 'CommandOrControl+D');
   assert.equal(config.shortcuts.toggleSubtitleSidebar, 'Backslash');
+  assert.equal(config.shortcuts.toggleNotificationHistory, 'CommandOrControl+N');
   assert.equal(config.discordPresence.enabled, true);
   assert.equal(config.discordPresence.updateIntervalMs, 3_000);
   assert.equal(config.subtitleStyle.backgroundColor, 'transparent');

src/config/definitions/defaults-core.ts

@@ -102,7 +102,7 @@ export const CORE_DEFAULT_CONFIG: Pick<
     openControllerSelect: 'Alt+C',
     openControllerDebug: 'Alt+Shift+C',
     toggleSubtitleSidebar: 'Backslash',
-    toggleNotificationHistory: 'Ctrl+N',
+    toggleNotificationHistory: 'CommandOrControl+N',
   },
   secondarySub: {
     secondarySubLanguages: [],

src/renderer/style.css

@@ -175,7 +175,7 @@ body:focus-visible,
   flex-direction: column;
   gap: 8px;
   pointer-events: auto;
-  z-index: 2147483647;
+  z-index: 2147483647 !important;
 }
 
 .overlay-notification-stack.position-top-left {