Draft: EasyMagpieTTS NeMo-RL hooks for vLLM-Omni

[vmendelev]

Draft handoff PR for the EasyMagpieTTS NeMo-RL + vLLM-Omni review branch.

Source branch: codex/easymagpie-grpo-review-omni
Base branch: easymp_vllm_omni
Accepted commit: 180fff16d2862dd2e8cd59ec2337d30a51e242f7

This branch contains the vLLM-Omni side of the EasyMagpieTTS GRPO recipe used by the accepted v564 gate:

• no-CFG fixed-speaker EasyMagpie generation path;
• online generated audio-code logprobs and stable stop/EOS metadata;
• runtime reset and live refit/update hooks for NeMo-RL rollouts;
• focused tests for the EasyMagpie vLLM-Omni integration.

The paired NeMo-RL branch is codex/easymagpie-grpo-review-core in https://gitlab-master.nvidia.com/vmendelev/nemo-rl.git at 9587c63e897d7ccfcf199e338ac90199f9df8eaf.

Validation reference: v564, 1 EOS node / 8 GPUs, 3 real GRPO update/refit steps, 1536 rollout candidates, Gemini raw input_audio plus Parakeet ASR quality gate passed on selected train/post-refit WAVs.