Refresh Qwen3.5 GB300 TRT-LLM AgentX metrics (#2770)

* config(qwen3.5): enable TRT-LLM AgentX metrics

* chore: add Qwen3.5 metrics refresh changelog

* fix(qwen3.5): require iteration metrics

* fix(agentx): aggregate TensorRT-LLM metrics

* fix(trtllm): decouple metrics from KV events

* Avoid detailed TRT metrics overhead

* Use metrics-only Dynamo publisher

* docs: consolidate metrics refresh changelog [skip-sweep]