fix: smooth book navigation by preventing view remount on bookId change

client/src/components/AppLayout.vue

@@ -10,6 +10,9 @@ const route = useRoute()
 const themeStore = useThemeStore()
 
 const backgroundClass = computed(() => BACKGROUND_OPTIONS.find((b) => b.id === themeStore.background)?.cssClass ?? '')
+
+const BOOK_ROUTE_NAMES = new Set(['book-detail', 'book-edit', 'book-files'])
+const viewKey = computed(() => (BOOK_ROUTE_NAMES.has(String(route.name)) ? String(route.name) : route.path))
 </script>
 
 <template>
@@ -21,7 +24,7 @@ const backgroundClass = computed(() => BACKGROUND_OPTIONS.find((b) => b.id === t
 
       <!-- 2. Independent View Area: Everything below the header scrolls here -->
       <div class="px-4 pt-2 flex-1 overflow-y-auto overflow-x-hidden relative scroll-smooth bg-transparent">
-        <router-view :key="route.path" />
+        <router-view :key="viewKey" />
         <!-- Bottom gutter matching the top floating margin -->
         <div class="h-6 w-full" />
       </div>

client/src/features/book/composables/useBookDetail.ts

@@ -10,7 +10,6 @@ export function useBookDetail() {
   async function fetch(bookId: number) {
     loading.value = true
     error.value = null
-    detail.value = null
     try {
       const res = await api(`/api/v1/books/${bookId}`)
       if (!res.ok) throw new Error(`HTTP ${res.status}`)