Function get_sync_sandbox_id 

pub fn get_sync_sandbox_id(
    corpus_id: i32,
    sandboxes: &SandboxCache,
    backend: &mut Backend,
) -> Option<i32>

Memoised getter for a corpus’s sandbox id, populating the shared SandboxCache from the backend on a miss (the ventilator’s DB-holding counterpart to get_sandbox_id). One lookup per corpus_id ever dispatched — bounded by the corpus count, not the task count.