feat(notifications): add overlay notifications with position config

- Add Catppuccin Macchiato overlay notification stack with 3s transient timeout
- Add `notifications.overlayPosition` config (top-left | top | top-right)
- Route startup tokenization and subtitle annotation status through configured surfaces
- Deduplicate rapid subtitle mode toggle notifications
- Change `both` to mean overlay + system; add `osd-system` as legacy alias for old behavior
- Keep `osd`/`osd-system` as config-file-only legacy values; Settings UI offers overlay/system/both/none

src/main/runtime/update/update-notifications.ts

@@ -1,7 +1,9 @@
 import type { UpdateNotificationType } from '../../../types/config';
+import type { OverlayNotificationPayload } from '../../../types/notification';
 
 export interface UpdateNotificationDeps {
   showSystemNotification: (title: string, body: string) => void;
+  showOverlayNotification: (payload: OverlayNotificationPayload) => void;
   showOsdNotification: (message: string) => void | Promise<void>;
   log: (message: string) => void;
 }
@@ -13,10 +15,14 @@ export async function notifyUpdateAvailable(
   if (options.notificationType === 'none') return;
 
   const message = `SubMiner v${options.version} is available`;
-  if (options.notificationType === 'system' || options.notificationType === 'both') {
-    deps.showSystemNotification('SubMiner update available', message);
+  if (options.notificationType === 'overlay' || options.notificationType === 'both') {
+    deps.showOverlayNotification({
+      title: 'SubMiner update available',
+      body: message,
+      variant: 'info',
+    });
   }
-  if (options.notificationType === 'osd' || options.notificationType === 'both') {
+  if (options.notificationType === 'osd' || options.notificationType === 'osd-system') {
     try {
       await deps.showOsdNotification(message);
     } catch (error) {
@@ -24,4 +30,11 @@ export async function notifyUpdateAvailable(
       deps.log(`Update OSD notification failed: ${reason}`);
     }
   }
+  if (
+    options.notificationType === 'system' ||
+    options.notificationType === 'both' ||
+    options.notificationType === 'osd-system'
+  ) {
+    deps.showSystemNotification('SubMiner update available', message);
+  }
 }