Use proper null utilities

Use dedicated null checking utilities like isDefined or isUndefinedOrNull instead of generic type coercion functions like Boolean(). Prefer undefined over empty strings or null as default values to maintain type safety and prevent runtime errors.

Avoid patterns like:

// Problematic
const isStreaming = Boolean(agentStreamingMessage) && streamData === agentStreamingMessage;
fieldName = '',  // empty string default
sourceHandle: null,  // explicit null

// Better
const isStreaming = isDefined(agentStreamingMessage) && streamData === agentStreamingMessage;
fieldName,  // undefined default
sourceHandle: DEFAULT_SOURCE_HANDLE_ID,  // meaningful default

This approach provides clearer intent, better type safety, and reduces the likelihood of runtime errors caused by unexpected falsy values.