Function validate_peft_config 

pub fn validate_peft_config(
    peft: &PeftAdapterConfig,
    max_lora_rank: usize,
) -> Result<()>

Adapter-config gates that need build-time context (--max-lora-rank). Parse-time gates (peft_type/DoRA/bias/regex target_modules/…) already ran in atlas_core::config::parse_peft_adapter_config.