fix UCX_ settings to fix nixl handshake failure

[biswapanda]

Note

Low Risk
Changes are limited to benchmark YAML env vars and an srt-slurm git branch for one model/framework combo; no application or auth logic is touched.

Overview
Updates MiniMax-M3 B300 FP8 disaggregated vLLM Slurm recipes so Nixl KV transfer can complete its UCX handshake instead of failing with the previous broad TLS/device settings.

On every affected 1k1k and 8k1k recipe, prefill and decode backend environments drop UCX_NET_DEVICES: "all" and replace UCX_TLS: "rc,cuda_ipc,cuda_copy,sm,self,tcp" with UCX_TLS: "cuda_copy,rc", matching the cluster’s mounted UCX stack used for these jobs.

For dynamo-vllm + minimaxm3 + fp8, launch_b300-nv.sh now checks out sa-submission-q2-2026 on srt-slurm instead of main before copying the in-repo MiniMax-M3 recipes.

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