Function appendTail

cli/src/runner/run.ts:437–444

(current: string, chunk: Buffer | string)

        const MAX_TAIL_CHARS = 4000;
        let stderrTail = '';
        const appendTail = (current: string, chunk: Buffer | string): string => {
          const text = chunk.toString();
          if (!text) {
            return current;
          }
          const combined = current + text;
          return combined.length > MAX_TAIL_CHARS ? combined.slice(-MAX_TAIL_CHARS) : combined;
        };
        const logStderrTail = () => {
          const trimmed = stderrTail.trim();
          if (!trimmed) {