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/types/runtime.ts

@@ -41,7 +41,7 @@ import type {
   RuntimeOptionState,
   RuntimeOptionValue,
 } from './runtime-options';
-import type { OverlayNotificationEventPayload } from './notification';
+import type { OverlayNotificationEventPayload, OverlayNotificationPosition } from './notification';
 
 export interface WindowGeometry {
   x: number;
@@ -408,6 +408,7 @@ export interface ElectronAPI {
   onOverlayPointerRecoveryRequested: (callback: () => void) => void;
   onOverlayNotification: (callback: (payload: OverlayNotificationEventPayload) => void) => void;
   sendOverlayNotificationAction?: (notificationId: string, actionId: string) => void;
+  onNotificationHistoryToggle: (callback: () => void) => void;
   onVisibility: (callback: (visible: boolean) => void) => void;
   onSubtitlePosition: (callback: (position: SubtitlePosition | null) => void) => void;
   getOverlayVisibility: () => Promise<boolean>;
@@ -436,6 +437,7 @@ export interface ElectronAPI {
   ) => Promise<void>;
   getStatsToggleKey: () => Promise<string>;
   getMarkWatchedKey: () => Promise<string>;
+  getOverlayNotificationPosition: () => Promise<OverlayNotificationPosition>;
   markActiveVideoWatched: () => Promise<boolean>;
   getControllerConfig: () => Promise<ResolvedControllerConfig>;
   saveControllerConfig: (update: ControllerConfigUpdate) => Promise<void>;