feat(desktop): toast "Mark as read" marks the room read (cinny-desktop #9)

Handles the native `lotus-notification-mark-read` event through the
same `markAsRead` path as the room menu's "Mark as Read", honouring the
private-receipt settings. Verified: 3 unread → 0 on the server.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA

src/app/hooks/useTauriToastActions.ts

@@ -5,6 +5,9 @@ import { Icons } from 'folds';
 import { useMatrixClient } from './useMatrixClient';
 import { useTauriEvent } from './useTauri';
 import { createErrorToast, toastQueueAtom } from '../state/toast';
+import { useSetting } from '../state/hooks/settings';
+import { settingsAtom } from '../state/settings';
+import { markAsRead } from '../utils/notifications';
 
 /** Payload of the `lotus-notification-activate` event (a plain body click). */
 interface ActivateDetail {
@@ -19,6 +22,11 @@ interface ReplyDetail {
   text?: string;
 }
 
+/** Payload of the `lotus-notification-mark-read` event (the Mark as read button). */
+interface MarkReadDetail {
+  roomId?: string;
+}
+
 /**
  * P5-41 / P5-35 — wire the native WinRT toast's click + quick-reply back into the
  * client. The Rust side (`show_rich_toast`) dispatches DOM CustomEvents via
@@ -27,12 +35,15 @@ interface ReplyDetail {
  *    the same `useNavigate(path)` mechanism the web `notificationclick` path uses
  *    (see ClientNonUIFeatures).
  *  - `lotus-notification-reply` → send the typed reply straight to the room.
+ *  - `lotus-notification-mark-read` → mark the room read, the same path as the
+ *    room menu's "Mark as Read" (cinny-desktop #9).
  * No-op outside Tauri (the events never fire).
  */
 export function useTauriToastActions(): void {
   const navigate = useNavigate();
   const mx = useMatrixClient();
   const setToast = useSetAtom(toastQueueAtom);
+  const [hideActivity] = useSetting(settingsAtom, 'hideActivity');
 
   useTauriEvent<ActivateDetail>('lotus-notification-activate', ({ path }) => {
     if (path) navigate(path);
@@ -55,4 +66,8 @@ export function useTauriToastActions(): void {
       );
     });
   });
+
+  useTauriEvent<MarkReadDetail>('lotus-notification-mark-read', ({ roomId }) => {
+    if (roomId) markAsRead(mx, roomId, hideActivity).catch(() => undefined);
+  });
 }