fix: Add null check for response ID to prevent memory leaks

- Check if response.id() is not null before processing in MCP session classes
- Log error when MCP response lacks session ID to warn about potential memory leaks
- Improve error handling in McpStreamableServerSession with proper error codes

The missing null check could lead to memory leaks as pending requests
would never be completed when responses lack session IDs. This fix ensures
proper handling of such cases with appropriate error logging.

Resolves #506

Signed-off-by: Yanming Zhou <zhouyanming@gmail.com>