Function remove_shared_if_nonce 

pub fn remove_shared_if_nonce(
    shared_dir: &Path,
    agent_id: &str,
    channel: &str,
    expected_nonce: u64,
)

remove_shared only if this channel’s entry was written by the spawn with expected_nonce — see remove_if_nonce (issue #2363). Cross-channel note: only this channel’s own file is read and removed, matching write_shared’s single-writer contract, so the process-local REGISTRY_OP_LOCK still suffices.