pipeline.ts large-spread RangeError

Trap: target.push(...source), Math.max(...map.keys()), and similar spreads look concise after size validation, but JavaScript’s engine-specific argument limit can throw RangeError well below permitted stream cardinality. Fix: append iteratively and compute bounded maxima in a loop, because valid many-item streams must still reach rollback, sanitization, accounting, and the fixed failure envelope.