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/app/api/blocks/[blockId]/status/route.ts

@@ -1,16 +1,7 @@
 import { NextRequest, NextResponse } from 'next/server'
 import prisma from '@/lib/prisma'
 import { auth } from '@/auth'
-
-function extractBlockContent(html: string, blockId: string): string | null {
-  const regex = new RegExp(
-    `<(?:p|h[1-6]|blockquote)[^>]*data-id="${blockId}"[^>]*>([\\s\\S]*?)<\\/(?:p|h[1-6]|blockquote)>`,
-    'i'
-  )
-  const match = regex.exec(html)
-  if (!match) return null
-  return match[1].replace(/<[^>]+>/g, '').trim()
-}
+import { extractBlockContentById } from '@/lib/blocks/extract-blocks'
 
 // GET /api/blocks/[blockId]/status?sourceNoteId=xxx
 export async function GET(
@@ -38,7 +29,7 @@ export async function GET(
     return NextResponse.json({ exists: false, content: '', sourceNoteTitle: '' })
   }
 
-  const content = extractBlockContent(note.content, blockId)
+  const content = extractBlockContentById(note.content, blockId)
 
   if (content === null) {
     return NextResponse.json({ exists: false, content: '', sourceNoteTitle: note.title || '' })