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/smart-paste-menu.tsx

@@ -0,0 +1,80 @@
+'use client'
+
+import { useEffect, useRef } from 'react'
+import { createPortal } from 'react-dom'
+import { useLanguage } from '@/lib/i18n'
+import { Link2, Blocks } from 'lucide-react'
+import type { ParsedBlockReference } from '@/lib/editor/parse-block-reference'
+
+export type SmartPasteMenuProps = {
+  anchor: { top: number; left: number }
+  reference: ParsedBlockReference
+  sourceNoteTitle?: string
+  onLive: () => void
+  onPlain: () => void
+  onClose: () => void
+}
+
+export function SmartPasteMenu({
+  anchor,
+  reference,
+  sourceNoteTitle,
+  onLive,
+  onPlain,
+  onClose,
+}: SmartPasteMenuProps) {
+  const { t } = useLanguage()
+  const menuRef = useRef<HTMLDivElement>(null)
+
+  useEffect(() => {
+    function handleClickOutside(e: MouseEvent) {
+      if (menuRef.current && !menuRef.current.contains(e.target as Node)) {
+        onClose()
+      }
+    }
+    function handleKeyDown(e: KeyboardEvent) {
+      if (e.key === 'Escape') onClose()
+    }
+    document.addEventListener('mousedown', handleClickOutside)
+    document.addEventListener('keydown', handleKeyDown)
+    return () => {
+      document.removeEventListener('mousedown', handleClickOutside)
+      document.removeEventListener('keydown', handleKeyDown)
+    }
+  }, [onClose])
+
+  const menuStyle: React.CSSProperties = {
+    position: 'fixed',
+    left: anchor.left,
+    top: anchor.top + 8,
+    zIndex: 9999,
+    maxWidth: 320,
+  }
+
+  if (Number(menuStyle.left) + 320 > window.innerWidth) {
+    menuStyle.left = Math.max(8, window.innerWidth - 328)
+  }
+  if (Number(menuStyle.top) + 140 > window.innerHeight) {
+    menuStyle.top = anchor.top - 132
+  }
+
+  const previewTitle = sourceNoteTitle?.trim() || t('smartPaste.unknownNote')
+
+  return createPortal(
+    <div ref={menuRef} style={menuStyle} className="block-action-menu smart-paste-menu">
+      <p className="smart-paste-menu__hint">{t('smartPaste.prompt')}</p>
+      <p className="smart-paste-menu__source" title={reference.raw}>
+        {previewTitle}
+      </p>
+      <button type="button" className="block-action-item" onClick={onLive}>
+        <Blocks size={16} />
+        <span>{t('smartPaste.liveBlock')}</span>
+      </button>
+      <button type="button" className="block-action-item" onClick={onPlain}>
+        <Link2 size={16} />
+        <span>{t('smartPaste.plainLink')}</span>
+      </button>
+    </div>,
+    document.body,
+  )
+}