explicitPath static method
The session the caller NAMED, by flag or by environment, or null when they named none.
The ownership check reads this rather than pathOverride alone. Both
spellings are documented as equivalent and path honours both, so a
guard that saw only the flag refused to drive the very session
ARTISAN_STATE_FILE had just pointed it at.
Implementation
static String? explicitPath() {
final String? flag = pathOverride;
if (flag != null && flag.isNotEmpty) return flag;
final String? env = _envPathOverride();
return (env != null && env.isNotEmpty) ? env : null;
}