Function resolve_env 

pub fn resolve_env(override_env: Option<&str>) -> String

Resolve the effective environment string.

Priority: explicit override > $GREENTIC_ENV > DEFAULT_ENV_ID ("local"). After resolution, applies the LEGACY_ENV_ID → DEFAULT_ENV_ID compat alias: any value of dev is remapped to local with a once-per-process tracing::warn! unless DISABLE_ALIAS_ENV_VAR is set, in which case the resolution panics with a remediation hint.