Function validate_signal 

pub fn validate_signal(signal: &str) -> Result<String>

Validate a signal name for Runtime::kill_container.

Accepts both the SIG-prefixed form ("SIGKILL") and the bare form ("KILL"). Returns the canonical uppercase SIG-prefixed name on success.

Errors

Returns AgentError::InvalidSpec when signal is not one of the supported signals: SIGKILL, SIGTERM, SIGINT, SIGHUP, SIGUSR1, SIGUSR2.