Function spawn_rpc_proxy_retyping_first_block_transaction 

pub async fn spawn_rpc_proxy_retyping_first_block_transaction(
    endpoint: String,
    tx_type: &'static str,
) -> String

Spawns an RPC proxy that reports the first transaction of every full block under tx_type.

Chains anvil can fork but not execute, such as Arbitrum and its Orbit rollups, open their blocks with a system transaction of a type Foundry does not model. This reproduces that shape on top of any endpoint, without depending on a public archive node.