Certified critical-line bound 0.673369430000000000000000000000

attempt-012 (Samuel Lavery, Apache-2.0) with the window re-optimised: v(s) = cos(sqrt2 s) + sum_{j=1}^{12} c_j cos(2 pi j s), the c_j chosen jointly with the six-point weights to maximise (H_W - B mu)/(1 - c mu) (typh). H_W >= 0.6721858656, B = 379691/10^8, c = 746194/10^8 within 0.01% of the minimum, m = 139. Theorem D for the window, the AM kernel evaluator and the seven-point engine are attempt-012's, re-proved for the new coefficients; the certificate data (pyramid, derivative tables, point table, convex regions, basins, walk: 10645 leaves) regenerated by typh. Proved constant >= 0.6733694349, candidate 67336943/10^8.