Text about decoupled reflection highlight and refraction direction unclear

1. in v1.2, when talking about `specular_weight`, it is unclear whether transmittance is affected. Fresnel factors contain both Fresnel reflectance and Fresnel transmittance. We should mention explicitly that only reflectance is affected, not the transmittance (which is not energy conserving?) and the refraction direction; or that both reflectance and transmittance are affected, but not the refraction direction.
2. When talking about dispersion, we say "We assume that `specular_ior` (including any modulation via specular_weight as in equation)", this pontentially contradicts the claim that refraction is unaffected. We need to clarify if/how modulated specular ior affects dispersion.

Start by locating the v1.2 passages about `specular_weight`, Fresnel factors, refraction direction, dispersion, and `specular_ior`, including the referenced equation. Compare the wording and equation so the specification explicitly resolves which quantities are affected; done means both ambiguities are clarified without contradicting claims elsewhere.

Written by the indexing model from the issue text.