[Model] Optimize Qwen3-Omni MRv2 handoff, code prediction and audio decoding (#8223)

Signed-off-by: Sy03 <1370724210@qq.com>

docs/design/index.md

@@ -116,4 +116,5 @@ The pre-#5137 pages are preserved in the
 [legacy module archive](module/archive/README.md) for historical reference and
 are not active design contracts.
 
+- [Qwen3-Omni MRv2 performance](qwen3_omni_mrv2_performance.md)
 - [MiniCPM-o 4.5 turn-mode MRv2 performance](minicpm_o45_mrv2_performance.md)

docs/design/qwen3_omni_mrv2_performance.md

@@ -0,0 +1,22 @@
+# Qwen3-Omni MRv2 performance
+
+This model adaptation builds on #8184's existing stage runtime and output
+contracts. It adds Talker CPU metadata parsing, sampled-token embedding
+handoff, an optional first-frame decoder, length-grouped Code2Wav graph
+buckets, and opt-in incremental short-KV code prediction. The H200 profile
+also enables conservative fused sampling and bounded cuDNN algorithm search.
+The shared predictor keeps the upstream re-prefill helper and its default
+sampling behavior; short KV is explicitly selected by the deployment profile.
+
+Use `vllm_omni/deploy/qwen3_omni_moe_mrv2_h200.yaml` for the experimental H200
+profile. Preserve a control with `code_predictor_fused_sampling=false` and
+`codec_cudnn_benchmark=false` when C64 P99 is the primary requirement.
+cuDNN search restores process settings on exit and has startup cost. Kernel
+arithmetic is not bitwise-equivalent; the first-frame decoder uses additional
+model memory. Full-duplex performance is not established by turn-mode tests.
+
+First-frame delivery requires `talker_first_audio: true` in connector extra,
+a one-frame initial codec chunk, CUDA, a local single-rank Talker and prefix caching disabled.
+Other deployments retain the regular Code2Wav path.
+`codec_fused_snake` explicitly opts CUDA profiles into fused decoder blocks;
+the base V1 profile retains its original blocks and indexed text cache.