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/universal/crypto.ts

@@ -11,7 +11,8 @@ let nodeCrypto: any = null
 // Dynamic import for Node.js crypto (only in Node.js environment)
 if (isNode()) {
   try {
-    nodeCrypto = await import('crypto')
+    // Use node: protocol to prevent bundler polyfilling (requires Node 22+)
+    nodeCrypto = await import('node:crypto')
   } catch {
     // Ignore import errors in non-Node environments
   }

src/universal/events.ts

@@ -11,7 +11,7 @@ let nodeEvents: any = null
 // Dynamic import for Node.js events (only in Node.js environment)
 if (isNode()) {
   try {
-    nodeEvents = await import('events')
+    nodeEvents = await import('node:events')
   } catch {
     // Ignore import errors in non-Node environments
   }

src/universal/fs.ts

@@ -11,7 +11,8 @@ let nodeFs: any = null
 // Dynamic import for Node.js fs (only in Node.js environment)
 if (isNode()) {
   try {
-    nodeFs = await import('fs/promises')
+    // Use node: protocol to prevent bundler polyfilling (requires Node 22+)
+    nodeFs = await import('node:fs/promises')
   } catch {
     // Ignore import errors in non-Node environments
   }

src/universal/path.ts

@@ -11,7 +11,8 @@ let nodePath: any = null
 // Dynamic import for Node.js path (only in Node.js environment)
 if (isNode()) {
   try {
-    nodePath = await import('path')
+    // Use node: protocol to prevent bundler polyfilling (requires Node 22+)
+    nodePath = await import('node:path')
   } catch {
     // Ignore import errors in non-Node environments
   }