Constant CWD_STATE_FILE_OVERRIDE_ENV 

const CWD_STATE_FILE_OVERRIDE_ENV: &str = "AGENTMUX_BASHWRAP_CWD_STATE_FILE";

bashwrap’s override for its cwd state file (crates/bashwrap/src/bash_wrap.rs, CWD_STATE_FILE_OVERRIDE_ENV). When a block’s env sets it, that is the file.