Function write_claim_grant 

pub async fn write_claim_grant<'c>(
    tx: &mut Transaction<'c, Postgres>,
    partition_key: i16,
    grant_key: &str,
    execution_id: Uuid,
    worker_id: &str,
    worker_instance_id: &str,
    grant_ttl_ms: u64,
    issued_at_ms: i64,
    expires_at_ms: i64,
) -> Result<(), EngineError>

Insert a fresh claim grant row. Called by the scheduler’s Stage 5.