feat: brainstorm sessions, PDF document Q&A, embedding fixes, and UI improvements

- Add brainstorm feature with collaborative canvas, AI idea generation, live cursors, playback, and export
- Add PDF upload/extraction/ingestion pipeline with pgvector document search (RAG)
- Add document Q&A overlay with streaming chat and PDF preview
- Add note attachments UI with status polling, grid layout, and auto-scroll
- Add task extraction AI tool and agent executor improvements
- Fix NoteEmbedding missing updatedAt column, re-index 66 notes with 1536-dim embeddings
- Fix brainstorm 'Create Note' button: add success toast and redirect to created note
- Fix memory echo notification infinite polling
- Fix chat route to always include document_search tool
- Add brainstorm i18n keys across all 14 locales
- Add socket server for real-time brainstorm collaboration
- Add hierarchical notebook selector and organize notebook dialog improvements
- Add sidebar brainstorm section with session management
- Update prisma schema with brainstorm tables, attachments, and document chunks

memento-note/components/memory-echo-notification.tsx

@@ -46,6 +46,7 @@ export function MemoryEchoNotification({ onOpenNote }: MemoryEchoNotificationPro
   const [fusionNotes, setFusionNotes] = useState<Array<Partial<Note>>>([])
   const [demoMode, setDemoMode] = useState(false)
   const pollingRef = useRef<ReturnType<typeof setInterval> | null>(null)
+  const dismissedPermanently = useRef(false)
 
   // Fetch insight on mount
   useEffect(() => {
@@ -63,8 +64,6 @@ export function MemoryEchoNotification({ onOpenNote }: MemoryEchoNotificationPro
 
       if (data.insight) {
         setInsight(data.insight)
-        // If we got an insight, check if user is in demo mode
-        setDemoMode(true)
       }
     } catch (error) {
       console.error('[MemoryEcho] Failed to fetch insight:', error)
@@ -73,28 +72,8 @@ export function MemoryEchoNotification({ onOpenNote }: MemoryEchoNotificationPro
     }
   }
 
-  // Start polling in demo mode after first dismiss
   useEffect(() => {
-    if (isDismissed && demoMode && !pollingRef.current) {
-      pollingRef.current = setInterval(async () => {
-        try {
-          const res = await fetch('/api/ai/echo')
-          const data = await res.json()
-          if (data.insight) {
-            setInsight(data.insight)
-            setIsDismissed(false)
-          }
-        } catch {
-          // silent
-        }
-      }, 15000) // Poll every 15s
-    }
-    return () => {
-      if (pollingRef.current) {
-        clearInterval(pollingRef.current)
-        pollingRef.current = null
-      }
-    }
+    if (dismissedPermanently.current) return
   }, [isDismissed, demoMode])
 
   const handleView = async () => {
@@ -158,6 +137,11 @@ export function MemoryEchoNotification({ onOpenNote }: MemoryEchoNotificationPro
 
   const handleDismiss = () => {
     setIsDismissed(true)
+    dismissedPermanently.current = true
+    if (pollingRef.current) {
+      clearInterval(pollingRef.current)
+      pollingRef.current = null
+    }
   }
 
   if (isLoading || !insight) {