Result of parseIdleTimeout: the resolved idle window plus an optional human-readable warning the caller should surface to the user.
const parsed: ParsedIdleTimeout = parseIdleTimeout('45s'); parsed.ms; // 45_000 parsed.warning; // null
ms: number
Milliseconds. Infinity when the user opts out of auto-shutdown via "false".
warning: string | null
Human-readable explanation, set when the env value was malformed. The caller
is expected to print this on the spawning CLI's stderr so the user sees it —
the daemon process detaches with stdio: 'ignore', so a warning emitted from
inside the daemon would be invisible.