fix: improve Node.js client streaming implementation

[vikhyat]

This PR fixes the skipped unit tests in the Node.js client and improves the streaming implementation.

Changes:

• Fix streaming implementation to properly handle Node.js streams
• Add proper TypeScript types for async iterator
• Fix tests to properly mock streaming response
• Make code more robust by handling both completion and end events
• Remove unnecessary buffering of chunks
• Add proper cleanup of event listeners

The key improvements are:

1. Real streaming - chunks are yielded as they arrive, not buffered
2. Better error handling - errors are properly propagated
3. Proper cleanup - event listeners are removed when done
4. Type safety - proper TypeScript types for all interfaces

All tests are now passing, including both unit tests and integration tests.