Generate the balanced 1,000-series tipping benchmark

Generate the balanced 1,000-series tipping benchmark

Produce 500 series approaching a fold bifurcation and 500 drifting-noise series of matched length and variance from a recorded seed. Seal the labels and the bifurcation times. Deliverable: A generator, 1,000 series files with checksums, and a sealed label file with series_id, class, and bifurcation_time.