Function uniqueNonNull

src/commands/test.ts:8302–8307

* If every non-null entry shares the same value, return it; otherwise * undefined. Used by step rendering to surface a per-response shared * `runId` / `codeVersion` once instead of in every row.

(values: Array<string | null>)

 * `runId` / `codeVersion` once instead of in every row.
 */
function uniqueNonNull(values: Array<string | null>): string | undefined {
  const filtered = values.filter((v): v is string => v !== null);
  if (filtered.length === 0) return undefined;
  const first = filtered[0]!;
  return filtered.every(v => v === first) ? first : undefined;
}

function pad(s: string, width: number): string {
  if (s.length >= width) return s;