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>

architectural-grid1/vite.config.ts

@@ -0,0 +1,24 @@
+import tailwindcss from '@tailwindcss/vite';
+import react from '@vitejs/plugin-react';
+import path from 'path';
+import {defineConfig, loadEnv} from 'vite';
+
+export default defineConfig(({mode}) => {
+  const env = loadEnv(mode, '.', '');
+  return {
+    plugins: [react(), tailwindcss()],
+    define: {
+      'process.env.GEMINI_API_KEY': JSON.stringify(env.GEMINI_API_KEY),
+    },
+    resolve: {
+      alias: {
+        '@': path.resolve(__dirname, '.'),
+      },
+    },
+    server: {
+      // HMR is disabled in AI Studio via DISABLE_HMR env var.
+      // Do not modify—file watching is disabled to prevent flickering during agent edits.
+      hmr: process.env.DISABLE_HMR !== 'true',
+    },
+  };
+});