feat: add node: protocol to all Node.js built-in imports for bundler compatibility

- Updated all fs, path, crypto, os, url, util, events, http, https, net, child_process, stream, and zlib imports
- Changed both static imports and dynamic imports to use node: protocol
- This makes Brainy more bundler-friendly by explicitly marking Node.js built-ins
- Prevents bundlers from attempting to polyfill or bundle these modules
- Reduces bundle size for web applications using Brainy
- Improves tree-shaking and dead code elimination

Benefits for external bundlers:
- Clear distinction between Node.js built-ins and external dependencies
- No ambiguity about what needs polyfilling
- Smaller bundles for browser builds
- Better compatibility with modern bundlers (Webpack 5, Vite, Rollup, esbuild)

🤖 Generated with Claude Code

Co-Authored-By: Claude <noreply@anthropic.com>

src/cli/catalog.ts

@@ -6,9 +6,9 @@
  */
 
 import chalk from 'chalk'
-import { readFileSync, writeFileSync, existsSync } from 'fs'
-import { join } from 'path'
-import { homedir } from 'os'
+import { readFileSync, writeFileSync, existsSync } from 'node:fs'
+import { join } from 'node:path'
+import { homedir } from 'node:os'
 
 const CATALOG_API = process.env.BRAINY_CATALOG_URL || null
 const CACHE_PATH = join(homedir(), '.brainy', 'catalog-cache.json')