Fix: Pass header parameter to StreamableHTTPClientTransport in MCPSessionManager

[viniychuk]

Summary

This PR fixes a bug in MCPSessionManager where the header parameter from StreamableHTTPConnectionParams was not being passed to the StreamableHTTPClientTransport constructor. This prevented authentication headers (like Authorization) from being sent to MCP servers over HTTP.

Changes

• Modified MCPSessionManager.createSession() to wrap the header parameter in a requestInit object
• Pass the requestInit object as the second argument to StreamableHTTPClientTransport

Testing

• Built the project successfully with npm run build
• Verified that the TypeScript types are correct

Impact

This enables users to authenticate with MCP servers that require authentication headers, such as Bearer tokens.

Example Usage

After this fix, users can pass authentication headers like this:
```typescript
const mcpToolset = new MCPToolset({
type: 'StreamableHTTPConnectionParams',
url: 'http://localhost:3001/mcp',
header: { 'Authorization': 'Bearer ' }
}, ['tool_name']);
```

Fixes authentication issues with StreamableHTTP MCP servers that require API keys or Bearer tokens.

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[viniychuk]

This addresses #33. Since header argument is unused anyways, could be an opportunity to rename it to headers, which feels more appropriate and matches RequestInit.

[kalenkevich]

Thanks!

[JonasPardon]

This addresses #33. Since header argument is unused anyways, could be an opportunity to rename it to headers, which feels more appropriate and matches RequestInit.

+1 from me, the argument being named headers feels more appropriate to me as well, first thing I noticed when trying out this package.

[ScottMansfield]

I'm ok changing the name but let's keep the PRs small and focused. You can open another if you want or just create the issue. Thank you for finding that, it looks like an inconsistency with the other ADKs, too.

Edit: It looks like you merged main into your branch, but we want to do single commit PRs. If you fast forward your branch it should pass the check again.

[JonasPardon]

@ScottMansfield any chance of you tagging a release for this? 🙏🏻