feat(renderer): PDF viewer with page nav & zoom controls (M10.2)

- PdfViewer.vue: lazy-loads pdfjs-dist, renders to canvas
- Page navigation (arrows), zoom controls (50%–200%)
- Keyboard navigation (arrow keys)
- Integrated into content panel via openPdfViewer()

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

packages/app/src/components/content/ContentPanel.vue

@@ -93,6 +93,12 @@
             :title="longFormArticle.title"
             @back="closeLongFormArticle"
           />
+          <PdfViewer
+            v-else-if="pdfUrl"
+            :url="pdfUrl.url"
+            :title="pdfUrl.title"
+            @back="closePdfViewer"
+          />
 
           <!-- Grid views by active tab -->
           <component
@@ -177,6 +183,7 @@ import PodcastDetail from './PodcastDetail.vue'
 import NewsGrid from './NewsGrid.vue'
 import ArticleDetail from './ArticleDetail.vue'
 import ArticleReader from '@/components/renderers/ArticleReader.vue'
+import PdfViewer from '@/components/renderers/PdfViewer.vue'
 import MagazineGrid from './MagazineGrid.vue'
 import ProjectGrid from './ProjectGrid.vue'
 import NostrGrid from './NostrGrid.vue'
@@ -227,11 +234,13 @@ const {
   closeArticleDetail,
   longFormArticle,
   closeLongFormArticle,
+  pdfUrl,
+  closePdfViewer,
   closePanel,
 } = useContentPanel()
 
 const hasDetailOpen = computed(() =>
-  !!(selectedFilm.value || selectedBook.value || selectedTVSeries.value || selectedSong.value || selectedPodcast.value || selectedArticle.value || selectedDesignSystemItem.value || longFormArticle.value)
+  !!(selectedFilm.value || selectedBook.value || selectedTVSeries.value || selectedSong.value || selectedPodcast.value || selectedArticle.value || selectedDesignSystemItem.value || longFormArticle.value || pdfUrl.value)
 )
 
 const windowWidth = ref(window.innerWidth)