feat: add headers and context support for remote connections

[deepracticexs]

Summary

Add ability to pass custom authentication headers and business context when creating remote AgentX connections. This addresses the integration needs described in #192.

Features

🔐 Custom Headers

• Node.js: Headers sent during WebSocket handshake
• Browser: Headers sent as first authentication message (WebSocket API limitation)
• Supports static values, sync functions, and async functions

📦 Business Context

• Automatically inject business context (userId, tenantId, permissions, etc.) into all requests
• Context is merged into the data field of every request
• Request-level context can override global context
• Supports static values, sync functions, and async functions

Usage

import { createAgentX } from "agentxjs";

// Static configuration
const agentx = await createAgentX({
  serverUrl: "ws://localhost:5200",
  headers: { Authorization: "Bearer sk-xxx" },
  context: { userId: "123", tenantId: "abc" },
});

// Dynamic configuration (sync)
const agentx = await createAgentX({
  serverUrl: "ws://localhost:5200",
  headers: () => ({ Authorization: \`Bearer \${getToken()}\` }),
  context: () => ({ userId: getCurrentUser().id }),
});

// Dynamic configuration (async)
const agentx = await createAgentX({
  serverUrl: "ws://localhost:5200",
  headers: async () => ({ Authorization: \`Bearer \${await fetchToken()}\` }),
  context: async () => ({ userId: await getUserId() }),
});

Changes

• RemoteConfig: Add optional headers and context fields
• ChannelClientOptions: Add optional headers field
• WebSocketClient: Implement header passing for Node.js and browser
• createRemoteAgentX: Add context merging logic

Testing

All functionality has been validated:

• ✅ Static headers/context
• ✅ Dynamic functions (sync)
• ✅ Dynamic functions (async)
• ✅ Request-level context override
• ✅ TypeScript type checking
• ✅ ESLint validation

Test scripts available in temp/ directory:

• temp/test-server-headers.ts - Test WebSocket server
• temp/test-client-headers.ts - Comprehensive client tests
• temp/README-HEADERS-TEST.md - Documentation

Related

Closes #192