feat(notifications): add notification history panel and overlay UX fixes

- New toggleNotificationHistory (Ctrl+N) session-scoped history panel; slides in from same edge as notification stack
- Overlay error/recovery toast follows notifications.overlayPosition; stack and history side seeded at startup
- Cold managed background startup initializes tray and visible overlay shell before tokenization warmups finish
- Add Update button to overlay update-available notifications
- Fix Ctrl+S sentence-card flow: only Anki progress notification, no duplicate status toast
- Fix overlay notification close/actions clickability above subtitle bars on Linux
- Increase pause-until-ready default timeout from 15s to 30s

src/main/runtime/composers/ipc-runtime-composer.test.ts

@@ -58,6 +58,7 @@ test('composeIpcRuntimeHandlers returns callable IPC handlers and registration b
         dispatchSessionAction: async () => {},
         getStatsToggleKey: () => 'Backquote',
         getMarkWatchedKey: () => 'KeyW',
+        getOverlayNotificationPosition: () => 'top-right',
         getControllerConfig: () => ({}) as never,
         saveControllerConfig: () => {},
         saveControllerPreference: () => {},