feat(app): add always-visible Prompt tab with magazine brief style

Adds a 'Prompt' tab that is always present as the rightmost tab in the
content panel. Shows the user's original query as a single magazine-style
tile using the existing MagazineGrid component.

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

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

@@ -72,6 +72,13 @@
     <NostrGrid
       v-else-if="activeTab === 'nostr'"
     />
+    <MagazineGrid
+      v-else-if="activeTab === 'prompt'"
+      :sections="[{ title: panelQuery || 'Your Prompt', content: panelQuery }]"
+      :hero-image-url="null"
+      title="Prompt"
+      :query="panelQuery"
+    />
   </div>
 </template>
 

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

@@ -348,6 +348,7 @@ const TAB_LABELS: Record<ContentTab, string> = {
   nostr: 'Nostr',
   favorites: 'Favorites',
   discover: 'Discover',
+  prompt: 'Prompt',
 }
 
 function tabLabel(tab: ContentTab): string {