Function LookupCommandContributingExtension 

fn LookupCommandContributingExtension(
    Environment: &MountainEnvironment,
    CommandIdentifier: &str,
) -> bool

Return true when some scanned extension declares onCommand:<CommandIdentifier> as one of its activation events. Used by the lazy-activation fallback in ExecuteCommand - without this check we’d fire an $activateByEvent("onCommand:X") for every unknown command, which would cause Cocoon to log “no extension matching event” for every typo. Scans the cached registry; no IPC.