text: Title: [Bug]: LLM.collective_rpc is broken in v1 by default
  Body: ### Your current environment
  
  v0.8.1
  
  ### 🐛 Describe the bug
  
  see https://github.com/vllm-project/vllm/pull/15324#discussion_r2008716131 for details.
  
  because `self.llm_engine.model_executor` is in a different process.
  
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