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/package.json

@@ -61,9 +61,13 @@
     "@stripe/react-stripe-js": "^6.3.0",
     "@stripe/stripe-js": "^9.5.0",
     "@tanstack/react-query": "^5.100.9",
+    "@tiptap/extension-collaboration": "^3.23.6",
     "@tiptap/extension-color": "^3.22.5",
+    "@tiptap/extension-drag-handle": "^3.23.6",
+    "@tiptap/extension-drag-handle-react": "^3.23.6",
     "@tiptap/extension-highlight": "^3.22.5",
     "@tiptap/extension-image": "^3.22.5",
+    "@tiptap/extension-node-range": "^3.23.6",
     "@tiptap/extension-placeholder": "^3.22.5",
     "@tiptap/extension-subscript": "^3.22.5",
     "@tiptap/extension-superscript": "^3.22.5",
@@ -80,6 +84,7 @@
     "@tiptap/react": "^3.22.5",
     "@tiptap/starter-kit": "^3.22.5",
     "@tiptap/suggestion": "^3.22.5",
+    "@tiptap/y-tiptap": "^3.0.3",
     "@types/d3": "^7.4.3",
     "@types/jsdom": "^28.0.1",
     "ai": "^6.0.23",
@@ -132,7 +137,11 @@
     "stripe": "^22.1.1",
     "tailwind-merge": "^3.4.0",
     "tinyld": "^1.3.4",
+    "tiptap-extension-auto-joiner": "^0.1.3",
+    "tiptap-extension-global-drag-handle": "^0.1.18",
     "vazirmatn": "^33.0.3",
+    "y-protocols": "^1.0.7",
+    "yjs": "^13.6.30",
     "zod": "^4.3.5"
   },
   "devDependencies": {