span_slack and af_snoise each spelled 2^-14 (value) and 2^-12 (gradient) inline, in C# and
HLSL. Both now read the constants beside SNOISE_HESSIAN (math.Affine.cs, CultMath.Affine.hlsl,
Unity copies), so a device-judged widening moves every reader. Bits unchanged. The test
oracles in AffineTests and GlslMirrorTests read the constants; a new test pins af_snoise's
allowance to span_slack's terms. span_slack's comment no longer claims it is the only
allowance. Does not build green yet: CultMath.glsl is not regenerated in this commit.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>