Constant ENV_DEVSHELL_VM 

pub const ENV_DEVSHELL_VM: &str = "DEVSHELL_VM";

DEVSHELL_VM — Release / binary default: unset means on (use VM backend per ENV_DEVSHELL_VM_BACKEND).

Set to off / 0 / false / no (case-insensitive) to use only the host temp sandbox. on / 1 / true / yes also enable VM mode.

Unit tests (cfg(test)): unset defaults to off so cargo test works without Lima.