Function validate_restored_history 

pub async fn validate_restored_history(
    messages: &[SharedMessage],
    state: &SharedContinuation,
    binding: &MemoryBinding,
) -> Result<()>

Host-only async pre-inference barrier for resumed Axel context heads. Call even when automatic management is off: mode is not evidence of durability. No hidden note is fetched or injected during validation. A failed lookup leaves the barrier pending, and resetting the binding invalidates late work.