Type Alias ValidationResult<T>

ValidationResult:
| { issues: readonly []; ok: true; options: T }
| { issues: readonly OptionIssue[]; ok: false }

What validateOptions gives back: the resolved options, or everything wrong with them.

A discriminated union rather than { issues, options? }, so a caller that checks ok gets the resolved options without a second narrowing step, and one that forgets cannot read an options that was never produced.