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/interactive.ts

@@ -371,7 +371,7 @@ export async function promptFileOrUrl(
       const data = await promptDataInput('import')
       // Save to temp file and return path
       const tmpFile = `/tmp/brainy-import-${Date.now()}.json`
-      const { writeFileSync } = await import('fs')
+      const { writeFileSync } = await import('node:fs')
       writeFileSync(tmpFile, data)
       return tmpFile
     default:
@@ -392,7 +392,7 @@ async function promptFilePath(action: string): Promise<string> {
         return 'Please enter a file path'
       }
       
-      const { existsSync } = await import('fs')
+      const { existsSync } = await import('node:fs')
       if (action === 'import' && !existsSync(input)) {
         return `File not found: ${input}`
       }