TwoProngHullSplitsTheScatterAcrossBothIntervals's own within-prong check
(atNearColumn > atFarColumn) held under M12/M12b (an entire second silhouette
built at the wrong sigma) and the sigma/sqrt(2) Stryker mutants, because every
wrong sigma tried still puts more mass on the nearer column -- direction alone
cannot separate a sigma of 1.5 from 1.5*sqrt(2). Their analytic near/far mass
ratios are well apart (~2.9 true vs ~1.73 at sigma*sqrt(2)), so the test now
computes the true ratio from the same per-cell Gaussian integral it already
uses and asserts the empirical ratio (8000 shots) tracks it within a tolerance
that rejects the wrong-sigma ratio.
Manually verified against the exact M12 and M12b patches from Soul's mutation
script: both now fail this test (empirical ratios 581 and 1.68, matching a
collapsed and a sqrt(2)-shifted sigma respectively, against the analytic ~2.9).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
c2b27b10ee