@ag-ui/client - textMessageBuffer not populated when emitting events directly

When extending AbstractAgent and emitting TEXT_MESSAGE_* events directly via the subscriber (not through HttpAgent with a server), the textMessageBuffer parameter passed to onTextMessageContentEvent is empty/undefined.

This appears to be because textMessageBuffer is computed by defaultApplyEvents which looks up the message content in the managed messages array. When events are emitted directly without going through defaultApplyEvents, no message objects are created, so the buffer lookup fails.

Questions:

Is this the intended behavior?
Should AbstractAgent maintain its own text buffer for direct event emission use cases?
Should the documentation clarify that textMessageBuffer only works when using the built-in event processing pipeline?

As a workaround I am manually accumulating deltas in an onEvent handler