on_llm_new_token

Intentional no-op — v1 chunks are not used on v2-flagged runs.

The v2 marker already steers invoke to the event generator, so on_llm_new_token should not fire under normal routing. This override stays a pass-through (no call to super()) to make the intent explicit and to guard against any caller (e.g. a node that calls model.stream() directly, which still fires the v1 callback) leaking AIMessageChunks onto a v2-flagged messages stream.