feat: editor improvements and architectural grid prototype

Multiple feature additions and improvements across the application:

- NextGen Editor: drag handles, smart paste, block actions
- Structured views: Kanban and table layouts for notes
- Architectural Grid: new brainstorming/agent interface prototype
- Flashcards: SM-2 revision algorithm with AI generation
- MCP server: robustness improvements
- Graph/PDF chat: fix click propagation and copy behavior
- Various UI/UX enhancements and bug fixes

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

memento-note/components/note-editor/note-editor-peek-host.tsx

@@ -0,0 +1,90 @@
+'use client'
+
+import { useState, useEffect, useCallback, type ReactNode } from 'react'
+import { AnimatePresence } from 'framer-motion'
+import { useRouter, useSearchParams } from 'next/navigation'
+import { toast } from 'sonner'
+import type { Note } from '@/lib/types'
+import { getNoteById } from '@/app/actions/notes'
+import { NOTE_REQUEST_SAVE_EVENT } from '@/lib/note-change-sync'
+import {
+  NOTE_PEEK_OPEN_EVENT,
+  NOTE_PEEK_CLOSE_EVENT,
+  type NotePeekOpenDetail,
+} from '@/lib/note-peek-sync'
+import { NoteEditorSplitPeek } from './note-editor-split-peek'
+import { useLanguage } from '@/lib/i18n'
+
+interface NoteEditorPeekHostProps {
+  noteId: string
+  fullPage?: boolean
+  children: ReactNode
+}
+
+export function NoteEditorPeekHost({ noteId, fullPage, children }: NoteEditorPeekHostProps) {
+  const router = useRouter()
+  const searchParams = useSearchParams()
+  const { t, language } = useLanguage()
+  const isRtl = language === 'fa' || language === 'ar'
+  const [peekState, setPeekState] = useState<{ note: Note; blockId?: string } | null>(null)
+
+  useEffect(() => {
+    const onOpenPeek = (event: Event) => {
+      const detail = (event as CustomEvent<NotePeekOpenDetail>).detail
+      if (!detail?.noteId) return
+      if (detail.noteId === noteId) return
+
+      void getNoteById(detail.noteId).then((fetched) => {
+        if (fetched) {
+          setPeekState({ note: fetched, blockId: detail.blockId })
+        } else {
+          toast.error(t('notePeek.loadFailed'))
+        }
+      })
+    }
+    const onClosePeek = () => setPeekState(null)
+
+    window.addEventListener(NOTE_PEEK_OPEN_EVENT, onOpenPeek)
+    window.addEventListener(NOTE_PEEK_CLOSE_EVENT, onClosePeek)
+    return () => {
+      window.removeEventListener(NOTE_PEEK_OPEN_EVENT, onOpenPeek)
+      window.removeEventListener(NOTE_PEEK_CLOSE_EVENT, onClosePeek)
+    }
+  }, [noteId, t])
+
+  const handleClosePeek = useCallback(() => {
+    setPeekState(null)
+  }, [])
+
+  const handleOpenPeekFully = useCallback(() => {
+    if (!peekState) return
+    window.dispatchEvent(new CustomEvent(NOTE_REQUEST_SAVE_EVENT, {
+      detail: { noteId, reason: 'before-peek-full-open' },
+    }))
+    const params = new URLSearchParams(searchParams.toString())
+    params.set('openNote', peekState.note.id)
+    router.replace(params.toString() ? `/home?${params.toString()}` : '/home', { scroll: false })
+    setPeekState(null)
+  }, [noteId, peekState, router, searchParams])
+
+  const shellClass = fullPage
+    ? 'flex flex-1 min-h-0 h-full w-full items-stretch overflow-hidden'
+    : 'relative flex min-h-0 flex-1 flex-col overflow-hidden'
+
+  return (
+    <div className={`${shellClass}${peekState ? (isRtl ? ' flex-row-reverse' : ' flex-row') : ''}`}>
+      <div className="flex-1 min-w-0 flex flex-col overflow-hidden">{children}</div>
+      <AnimatePresence initial={false}>
+        {peekState && (
+          <NoteEditorSplitPeek
+            key={peekState.note.id}
+            note={peekState.note}
+            blockId={peekState.blockId}
+            onClose={handleClosePeek}
+            onOpenFully={handleOpenPeekFully}
+          />
+        )}
+      </AnimatePresence>
+    </div>
+  )
+}