fix(reader): open books without a View Transition to avoid timeout (#4949)

useAppRouter wraps every navigation in a View Transition. Opening a book is a
heavy render (the reader mounts and loads the book) that can overrun the
transition's ~4s DOM-update budget and abort with a TimeoutError (Sentry
READEST-9). Navigate to the reader with the plain router instead, matching
every other into-reader path in the app; the transition router stays for
lighter navigation. Applies to the tap-to-open flow (useOpenBook) and the
post-import queued open (library/page).

Fixes READEST-9

Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/readest-app/src/app/library/hooks/useOpenBook.ts

@@ -3,8 +3,8 @@ import { Book } from '@/types/book';
 import { useEnv } from '@/context/EnvContext';
 import { useLibraryStore } from '@/store/libraryStore';
 import { useSettingsStore } from '@/store/settingsStore';
+import { useRouter } from 'next/navigation';
 import { useTranslation } from '@/hooks/useTranslation';
-import { useAppRouter } from '@/hooks/useAppRouter';
 import { eventDispatcher } from '@/utils/event';
 import { navigateToReader, showReaderWindow } from '@/utils/nav';
 
@@ -25,7 +25,11 @@ interface UseOpenBookOptions {
  */
 export const useOpenBook = ({ setLoading, handleBookDownload }: UseOpenBookOptions) => {
   const _ = useTranslation();
-  const router = useAppRouter();
+  // Open the reader with the plain router, NOT the View Transition router:
+  // the reader's initial render is heavy enough to blow the transition's ~4s
+  // DOM-update budget, which aborts with a TimeoutError (Sentry READEST-9).
+  // This matches how every other into-reader path already navigates.
+  const router = useRouter();
   const { envConfig, appService } = useEnv();
   const { settings } = useSettingsStore();
   const { updateBook } = useLibraryStore();

apps/readest-app/src/app/library/page.tsx

@@ -4,7 +4,7 @@ import clsx from 'clsx';
 import * as React from 'react';
 import { MdChevronRight } from 'react-icons/md';
 import { useState, useRef, useEffect, Suspense, useCallback } from 'react';
-import { ReadonlyURLSearchParams, useSearchParams } from 'next/navigation';
+import { ReadonlyURLSearchParams, useRouter, useSearchParams } from 'next/navigation';
 
 import { Book } from '@/types/book';
 import { AppService, DeleteAction } from '@/types/system';
@@ -155,6 +155,10 @@ const LibraryPageWithSearchParams = () => {
 
 const LibraryPageContent = ({ searchParams }: { searchParams: ReadonlyURLSearchParams | null }) => {
   const router = useAppRouter();
+  // Opening the reader is a heavy render that overruns the View Transition
+  // DOM-update budget (TimeoutError, Sentry READEST-9), so navigate to it with
+  // the plain router; `router` above keeps transitions for lighter navigation.
+  const readerRouter = useRouter();
   const { envConfig, appService } = useEnv();
   const { token, user } = useAuth();
   const {
@@ -568,10 +572,10 @@ const LibraryPageContent = ({ searchParams }: { searchParams: ReadonlyURLSearchP
       const bookIds = pendingNavigationBookIds;
       setPendingNavigationBookIds(null);
       if (bookIds.length > 0) {
-        navigateToReader(router, bookIds);
+        navigateToReader(readerRouter, bookIds);
       }
     }
-  }, [pendingNavigationBookIds, appService, router]);
+  }, [pendingNavigationBookIds, appService, readerRouter]);
 
   useEffect(() => {
     if (isInitiating.current) return;