Function picker_for_environment 

pub fn picker_for_environment(has_llm: bool) -> MutatorPicker

Build the mutator picker, omitting LLM-dependent mutators if no LLM is reachable. Without this, the default 50%-LLM-rewrite weight means roughly half of all challenger generations would silently fail to mutate anything when the user has no Anthropic key and no local Ollama.