feat(playground): add Node.js ESM example for KaibanJS

- Created a new playground example demonstrating KaibanJS usage in Node.js
- Implemented both ESM and CommonJS versions of a team workflow
- Added comprehensive README with setup instructions and code examples
- Included .env.example for API key configuration
- Set up package.json with scripts for running ESM and CJS versions

playground/nodejs-esm/.env.example

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+# OpenAI API Key for KaibanJS
+OPENAI_API_KEY=your-api-key-here 

playground/nodejs-esm/README.md

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+# Node.js ESM Example
+
+This example demonstrates using KaibanJS in a Node.js environment with ESM (ECMAScript Modules) imports. It includes both ESM and CommonJS versions of the same code to showcase compatibility across different module systems.
+
+## Environment Setup
+
+- Node.js version: >=21.0.0 (tested with Node.js 21)
+- KaibanJS version: ^0.14.0
+
+## Project Structure
+
+```
+nodejs-esm/
+├── .env                 # Environment variables configuration
+├── index.js            # ESM version using import statements
+├── index.cjs           # CommonJS version using require statements
+└── package.json        # Project configuration with "type": "module"
+```
+
+## Key Features
+
+- Demonstrates KaibanJS usage in a Node.js environment
+- Shows both ESM and CommonJS module system compatibility
+- Implements a complete team workflow with multiple agents and tasks
+- Includes proper error handling and workflow status monitoring
+
+## Getting Started
+
+1. Install dependencies:
+   ```bash
+   npm install
+   ```
+
+2. Configure your environment:
+   - Copy `.env.example` to `.env` (if not already done)
+   - Add your OpenAI API key to `.env`:
+     ```
+     OPENAI_API_KEY=your-api-key-here
+     ```
+
+3. Run the examples:
+   ```bash
+   # Run ESM version
+   npm start
+
+   # Run CommonJS version
+   npm run start:cjs
+   ```
+
+## Code Examples
+
+### ESM Version (index.js)
+```javascript
+import { Agent, Task, Team } from 'kaibanjs';
+```
+
+### CommonJS Version (index.cjs)
+```javascript
+const { Agent, Task, Team } = require('kaibanjs');
+```
+
+## Notes
+
+- This example demonstrates that KaibanJS works in Node.js environments without requiring React as a dependency
+- The example uses zustand's core functionality without React-specific features
+- Both ESM and CommonJS versions implement the same functionality to showcase module system compatibility 

playground/nodejs-esm/index.cjs

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+// CommonJS version
+const { Agent, Task, Team } = require('kaibanjs');
+const dotenv = require('dotenv');
+
+dotenv.config();
+
+// Create multiple agents with different roles
+const researcher = new Agent({
+  name: 'ResearchBot',
+  role: 'Research Specialist',
+  goal: 'Gather and analyze information',
+  background: 'Expert in data collection and analysis',
+});
+
+const writer = new Agent({
+  name: 'WriterBot',
+  role: 'Content Writer',
+  goal: 'Create engaging content from research',
+  background: 'Professional content creator and editor',
+});
+
+const reviewer = new Agent({
+  name: 'ReviewBot',
+  role: 'Quality Reviewer',
+  goal: 'Ensure content meets quality standards',
+  background: 'Quality assurance specialist',
+});
+
+// Create tasks for each agent
+const researchTask = new Task({
+  title: 'Research Topic',
+  description: 'Research the given topic and extract key information',
+  expectedOutput: 'Structured research data',
+  agent: researcher,
+});
+
+const writingTask = new Task({
+  title: 'Create Content',
+  description: 'Transform research into engaging content',
+  expectedOutput: 'Draft content',
+  agent: writer,
+});
+
+const reviewTask = new Task({
+  title: 'Review Content',
+  description: 'Review and polish the content',
+  expectedOutput: 'Final polished content',
+  agent: reviewer,
+});
+
+// Create and configure the team
+const team = new Team({
+  name: 'Content Creation Team',
+  agents: [researcher, writer, reviewer],
+  tasks: [researchTask, writingTask, reviewTask],
+  inputs: {
+    topic:
+      'The impact of artificial intelligence on modern software development',
+  },
+  env: { OPENAI_API_KEY: process.env.OPENAI_API_KEY },
+});
+
+// Subscribe to team status updates
+const unsubscribe = team.subscribeToChanges(
+  (updatedFields) => {
+    console.log('Team Status Updated:', updatedFields);
+  },
+  ['teamWorkflowStatus']
+);
+
+// Start the team workflow
+console.log('Starting team workflow...');
+(async () => {
+  try {
+    const result = await team.start();
+    console.log('Final Result:', result);
+  } catch (error) {
+    console.error('Error during workflow:', error);
+  } finally {
+    unsubscribe();
+  }
+})();

playground/nodejs-esm/index.js

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+// ESM version
+import { Agent, Task, Team } from 'kaibanjs';
+import * as dotenv from 'dotenv';
+
+dotenv.config();
+
+// Create multiple agents with different roles
+const researcher = new Agent({
+  name: 'ResearchBot',
+  role: 'Research Specialist',
+  goal: 'Gather and analyze information',
+  background: 'Expert in data collection and analysis',
+});
+
+const writer = new Agent({
+  name: 'WriterBot',
+  role: 'Content Writer',
+  goal: 'Create engaging content from research',
+  background: 'Professional content creator and editor',
+});
+
+const reviewer = new Agent({
+  name: 'ReviewBot',
+  role: 'Quality Reviewer',
+  goal: 'Ensure content meets quality standards',
+  background: 'Quality assurance specialist',
+});
+
+// Create tasks for each agent
+const researchTask = new Task({
+  title: 'Research Topic',
+  description: 'Research the given topic and extract key information',
+  expectedOutput: 'Structured research data',
+  agent: researcher,
+});
+
+const writingTask = new Task({
+  title: 'Create Content',
+  description: 'Transform research into engaging content',
+  expectedOutput: 'Draft content',
+  agent: writer,
+});
+
+const reviewTask = new Task({
+  title: 'Review Content',
+  description: 'Review and polish the content',
+  expectedOutput: 'Final polished content',
+  agent: reviewer,
+});
+
+// Create and configure the team
+const team = new Team({
+  name: 'Content Creation Team',
+  agents: [researcher, writer, reviewer],
+  tasks: [researchTask, writingTask, reviewTask],
+  inputs: {
+    topic:
+      'The impact of artificial intelligence on modern software development',
+  },
+  env: { OPENAI_API_KEY: process.env.OPENAI_API_KEY },
+});
+
+// Subscribe to team status updates
+const unsubscribe = team.subscribeToChanges(
+  (updatedFields) => {
+    console.log('Team Status Updated:', updatedFields);
+  },
+  ['teamWorkflowStatus']
+);
+
+// Start the team workflow
+console.log('Starting team workflow...');
+try {
+  const result = await team.start();
+  console.log('Final Result:', result);
+} catch (error) {
+  console.error('Error during workflow:', error);
+} finally {
+  unsubscribe();
+}