feat: add universal adapters for browser compatibility

- Create universal adapters for cross-platform support (browser/Node/serverless)
- Replace Node.js-specific imports with universal implementations
- Add OPFS support for browser persistent storage
- Maintain same BrainyData interface across all environments
- Enable real Brainy usage in browser console UI
- Keep package size optimized (no bloat)

Universal adapters in /src/universal/:
- uuid.ts: Cross-platform UUID generation
- crypto.ts: Browser/Node crypto operations
- fs.ts: OPFS/FileSystem/Memory storage adapter
- path.ts: Universal path operations
- events.ts: EventEmitter compatibility layer

This enables 'write once, run anywhere' for Brainy while maintaining
the exact same API. No breaking changes to existing code.

src/universal/path.ts

@@ -0,0 +1,187 @@
+/**
+ * Universal Path implementation
+ * Browser: Manual path operations
+ * Node.js: Uses built-in path module
+ */
+
+import { isNode } from '../utils/environment.js'
+
+let nodePath: any = null
+
+// Dynamic import for Node.js path (only in Node.js environment)
+if (isNode()) {
+  try {
+    nodePath = await import('path')
+  } catch {
+    // Ignore import errors in non-Node environments
+  }
+}
+
+/**
+ * Universal path operations
+ */
+export function join(...paths: string[]): string {
+  if (nodePath) {
+    return nodePath.join(...paths)
+  }
+  
+  // Browser fallback implementation
+  const parts: string[] = []
+  for (const path of paths) {
+    if (path) {
+      parts.push(...path.split('/').filter(p => p))
+    }
+  }
+  return parts.join('/')
+}
+
+export function dirname(path: string): string {
+  if (nodePath) {
+    return nodePath.dirname(path)
+  }
+  
+  // Browser fallback implementation
+  const parts = path.split('/').filter(p => p)
+  if (parts.length <= 1) return '.'
+  return parts.slice(0, -1).join('/')
+}
+
+export function basename(path: string, ext?: string): string {
+  if (nodePath) {
+    return nodePath.basename(path, ext)
+  }
+  
+  // Browser fallback implementation
+  const parts = path.split('/')
+  let name = parts[parts.length - 1]
+  
+  if (ext && name.endsWith(ext)) {
+    name = name.slice(0, -ext.length)
+  }
+  
+  return name
+}
+
+export function extname(path: string): string {
+  if (nodePath) {
+    return nodePath.extname(path)
+  }
+  
+  // Browser fallback implementation
+  const name = basename(path)
+  const lastDot = name.lastIndexOf('.')
+  return lastDot === -1 ? '' : name.slice(lastDot)
+}
+
+export function resolve(...paths: string[]): string {
+  if (nodePath) {
+    return nodePath.resolve(...paths)
+  }
+  
+  // Browser fallback implementation
+  let resolved = ''
+  let resolvedAbsolute = false
+  
+  for (let i = paths.length - 1; i >= -1 && !resolvedAbsolute; i--) {
+    const path = i >= 0 ? paths[i] : '/'
+    
+    if (!path) continue
+    
+    resolved = path + '/' + resolved
+    resolvedAbsolute = path.charAt(0) === '/'
+  }
+  
+  // Normalize the path
+  resolved = normalizeArray(resolved.split('/').filter(p => p), !resolvedAbsolute).join('/')
+  
+  return (resolvedAbsolute ? '/' : '') + resolved
+}
+
+export function relative(from: string, to: string): string {
+  if (nodePath) {
+    return nodePath.relative(from, to)
+  }
+  
+  // Browser fallback implementation
+  const fromParts = resolve(from).split('/').filter(p => p)
+  const toParts = resolve(to).split('/').filter(p => p)
+  
+  let commonLength = 0
+  for (let i = 0; i < Math.min(fromParts.length, toParts.length); i++) {
+    if (fromParts[i] === toParts[i]) {
+      commonLength++
+    } else {
+      break
+    }
+  }
+  
+  const upCount = fromParts.length - commonLength
+  const upParts = new Array(upCount).fill('..')
+  const downParts = toParts.slice(commonLength)
+  
+  return [...upParts, ...downParts].join('/')
+}
+
+export function isAbsolute(path: string): boolean {
+  if (nodePath) {
+    return nodePath.isAbsolute(path)
+  }
+  
+  // Browser fallback implementation
+  return path.charAt(0) === '/'
+}
+
+/**
+ * Normalize array helper function
+ */
+function normalizeArray(parts: string[], allowAboveRoot: boolean): string[] {
+  const res: string[] = []
+  for (let i = 0; i < parts.length; i++) {
+    const p = parts[i]
+    
+    if (!p || p === '.') continue
+    
+    if (p === '..') {
+      if (res.length && res[res.length - 1] !== '..') {
+        res.pop()
+      } else if (allowAboveRoot) {
+        res.push('..')
+      }
+    } else {
+      res.push(p)
+    }
+  }
+  
+  return res
+}
+
+// Path separator (always use forward slash for consistency)
+export const sep = '/'
+export const delimiter = ':'
+
+// POSIX path object for compatibility
+export const posix = {
+  join,
+  dirname,
+  basename,
+  extname,
+  resolve,
+  relative,
+  isAbsolute,
+  sep: '/',
+  delimiter: ':'
+}
+
+// Default export
+export default {
+  join,
+  dirname,
+  basename,
+  extname,
+  resolve,
+  relative,
+  isAbsolute,
+  sep,
+  delimiter,
+  posix
+}